Definition of flatten in English:

flatten

verb

1Make or become flat or flatter.
with object ‘spoon the mixture into the pan, flatten into cakes, and fry until brown’
no object ‘the ground flattened out and became marshy’
‘they were dancing on the flattened grass’
- ‘I mutter a sheepish apology and get to my feet, smoothing my shirt and trying to flatten my hair.’
- ‘His normally very tidy light brown hair had flattened in some areas and began to stick out in others.’
- ‘If your girlfriend has beautiful wavy hair, would you want her to flatten it out by combing it with the wrong brush?’
- ‘He attempted to flatten the hair without a comb.’
- ‘Secondly, the mixture is then flattened out in the blending machine, and then it is flattened further in an extruder machine.’
- ‘The foot and a half tall grass was flattened in their fight.’
- ‘The heavy boots he wore had long ago flattened and grass he walked on, making a perfectly straight path where he had paced for the past few hours.’
- ‘He is not a land artist, he flattens no grass and makes no patterns with twigs or boulders.’
- ‘Turn over the cake and flatten slightly, before slashing the top three times with a sharp knife.’
- ‘The rain pounded down on her, flattening the wild grasses and weeds around her.’
- ‘His regular spot was left empty, the grass he would normally flatten sitting upright and proud.’
- ‘Look at that mutilated cow in the field, and see that flattened grass.’
- ‘Peter combed his dark brown hair, trying to flatten the back and sides, but as usual it remained up turned.’
- ‘One was suddenly flung away and the grass flattened in a widening circle.’
- ‘She scowls and takes out her hairbrush and flattens her hair with quick, angry strokes.’
- ‘As children first introduced to the mysteries of the kitchen, we learn how to blend the batter of a cake or flatten the dough of a pie.’
- ‘If I manage to dodge it, it will still flatten the grass and leave it's mark.’
- ‘Laurie folded his feet and sat down, flattening the grass.’
- ‘And it just straightens her hair, flattens it out perfectly.’
- ‘She quickly brushed, combed, and flattened her hair.’
become flat, make flat, become even, make even, become smooth, make smooth, smooth, smooth off, smooth out, level, level off, level out, even out
compress, press down, crush, squash, compact
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1. 1.1with object and adverbial of place Press (oneself or one's body) against a surface, typically to get away from something or to let someone pass.
  ‘they flattened themselves on the pavement as a bomb came whistling down’
  ‘He flattened himself out on the floor and watched me.’
  ‘The four of them immediately flattened themselves against the wall.’
  ‘She nodded at a pretty brunette and flattened herself against the wall.’
  ‘In her haste, she almost ran over a ship's lieutenant, who flattened himself against the doorway as she charged past him.’
  ‘Nikki shrieked and flattened herself against the wall.’
  ‘In fact, Brittany completely flattened herself against the wall.’
  ‘She flattened herself against the treetrunk and waited.’
  ‘He has flattened himself violently against the wall, his knees bent in towards it, body shaking.’
  ‘Shane flattened himself against the side of the bookshelf backing onto where the guard would approach from and waited.’
  ‘At once he made for a tree and flattened himself against its bark.’
  ‘Thinking quickly, he flattened himself up against the wall next to the door, lying in wait.’
  ‘I heard a step of foot steps and flattened myself further up against the wall, looking in front of me to where the person was coming from.’
  ‘Panting, he flattened himself against a mold-streaked stone wall, praying it would be just another sentry.’
  ‘She winced and flattened herself more against the tree.’
  ‘Claria flattened herself against the wall, peering around a corner.’
  ‘I recoiled, eyes wide open and flattened myself to the bed.’
  ‘The five-year old flattened himself against the wall, whimpering.’
  ‘I flattened myself against the wall for dear life, and somehow, somehow, he never noticed me.’
  ‘A group of children noisily pushed through the crowd, so Jag flattened himself against the wall to keep from getting squashed.’
  ‘At the sound of a window opening on the second floor, above my head, a little to the right, I backed up and flattened myself against the door.’
2with object Raze (a building or settlement) to the ground.
‘the hurricane flattened thousands of homes’
- ‘The resulting explosion flattened the target building and the surrounding infrastructure, crushing the defenders.’
- ‘The blast had destroyed the wall of the cemetery and flattened a nearby home.’
- ‘There were no immediate details of casualties on the ground but witnesses said 12 houses were flattened in the disaster.’
- ‘Churches, mosques and school buildings are among the public facilities flattened by the quakes.’
- ‘A boat has managed to get to the south of the island but initial reports are that all the buildings are flattened.’
- ‘The army has used its newly acquired firepower to flatten houses and other buildings, destroy coconut plantations and turn the city into a virtual ghost town.’
- ‘Hurricanes bring winds and slashing rains that flood streets, flatten homes, and leave survivors struggling to pick up the pieces.’
- ‘Homes and public buildings were completely flattened.’
- ‘The storm, which also flattened several power pylons, left much of the Eastern Cape without electricity.’
- ‘Just 12 minutes after the order, the bombs were dropped from an altitude of 20,000 ft, flattening the building.’
- ‘But the torrent of brown water, which was already flattening buildings, wiped out the jeep, drowning her grandchildren.’
- ‘Workmen moved on to the site last week to flatten the building and replace it with 138 flats.’
- ‘These bombs vaporised all living life and flattened all buildings within the epicentre of the explosion.’
- ‘Traders were triumphant today after plans to flatten their homes and businesses were refused by council planners.’
- ‘Plans to flatten a listed building for a TV show have been branded ridiculous by the grandson of the man who built it.’
- ‘Thousands of houses were completely flattened, and many others were partially destroyed.’
- ‘Walls of houses were completely flattened; glass, bricks and debris are everywhere.’
- ‘It ripped off roofs, flattened buildings and threw container lorries great distances.’
- ‘Bulldozers could flatten buildings used to care for the elderly and disabled if a site near the town centre is sold off.’
- ‘A business that is hit hard during a recession is not unlike a business whose building is flattened by a tornado.’
demolish, raze, raze to the ground, level, tear down, knock down, destroy, wipe out, topple, wreck, reduce to ruins, devastate, annihilate, pulverize, obliterate, ravage, smash, wipe off the face of the earth, wipe off the map
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1. 2.1informal Knock someone down with power and vigor.
  ‘once I'm in the ring, I know I can flatten him’
  ‘So there I was in the paddock when I'm flattened by some idiot running into me on a monkey bike!’
  ‘You were lucky Brett didn't end up flattening you.’
  ‘I was about to wish for a rock to fall off the sky and flatten me into a very slow and painful death, when the doorbell rang.’
  ‘When former St Peter's schoolboy, James Dougherty, led a lone break-out he was flattened by an excellent Heppleston tackle.’
  ‘I considered, with idle horror, how a simple kick of my foot could flatten him beyond repair.’
  ‘I woke up cold and he tried to roll his body onto me and share his body heat and the sleeping bag, nearly flattening me in the process.’
  ‘The purpose of modernisation is to flatten the pyramid, to push power downwards and re-enfranchise the rank-and-file.’
  ‘The match exploded after a clash between Iain Hendry and Bromley's Mark Watson, who chased the Leatherhead man and flattened him, earning an instant red card.’
  ‘The next minute, she was flattened by a reversing car, leaving her with broken arms and legs.’
  ‘The guy was very fortunate as the big man could have flattened him.’
  ‘Kristie landed on him, flattening him against the floor.’
  ‘The scrum-half must have suspected a conspiracy - on three occasions in the first half he was flattened by opponents.’
  ‘He said: ‘The old guy looked in good shape and I'm sure he would have flattened the other guy - if he could have caught him.’’
  ‘He also mowed over his wife on the same day Maude flattened the child.’
  ‘Terrified I'd flatten a child, I picked my way between bodies, big and small, and noticed Sainabo cuddled up beside her mother.’
  ‘Luckily for him the ambulance was not travelling very fast, because he gave the paramedic driving it so little warning time that had it been going any faster it would have certainly flattened Patrick.’
  ‘In perhaps the turning point of the game, Steven Boyack flattened Dennis Wyness just inside the area in 18 minutes and Paul Sheerin powered in the penalty.’
  ‘A vision of me stepping on him, wobbling and then falling on him, flattening him like a pancake flashed through my head.’
  knock down, knock over, knock to the ground, knock off one's feet, fell, rugby-tackle, topple, prostrate
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2. 2.2informal Defeat (someone) completely, especially in a sports contest.
  beat, conquer, win against, win a victory over, triumph over, prevail over, get the better of, best, worst, vanquish
  loss, beating, conquest, conquering, besting, worsting, vanquishing, vanquishment, game, set, and match
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3Music
with object Lower (a note) in pitch by a half step.

Phrasal Verbs

flatten out

1(of an increasing quantity or rate) show a less marked rise; slow down.
- ‘On the other hand, the survey report will point out that the recent fall in unemployment is slowing, effectively flattening out over the past three months.’
- ‘However, this rate has flattened out in the past decade, although women's educational level continues to grow steadily.’
- ‘Eating at shorter intervals will also help flatten out excessive rises and dips in your blood sugar, which means you'll have energy available for use more consistently.’
- ‘We saw prices rise by about five or six per cent and the market flattened out a lot.’
- ‘If you're a retailer, for example, the hosting bills will likely surge during the holiday season but then flatten out during slow months.’
- ‘There was, as a result, no financial and industrial bankruptcy, but growth rates flattened out for the rest of the period, until they were restarted by the outbreak of the First World War.’
- ‘Despite an ongoing economic boom, Portland's housing cost increases flattened out after 1995, and now roughly match the rate of inflation.’
- ‘That asymptotic rise of the stock markets since WWII has flattened out.’
- ‘The long ‘plateau’ period where this rise in prosecutions flattened out is more difficult to explain.’
- ‘Both these trends have flattened out in recent years, with the rate increasing slightly in 1999 and 2000.’
2Make an aircraft fly horizontally after a dive or climb.
‘he flattened out and made a fine three-point landing’
- ‘People out fishing reported seeing the aircraft flying straight and level, then entering a spiral dive before flattening out momentarily.’
- ‘The Ju 88 went into a steep, jinking dive with the rear gunner firing at the other members of his Section who all attacked, until the Ju 88 flattened out and crash-landed at high speed.’