Definition of SMH in English:

SMH

informal
  • Shaking (or shake) my head (used to express disapproval, exasperation, frustration, etc.):

    ‘They'll do anything for ratings. SMH’
    ‘SMH at your silly remarks’
    ‘I can both understand the outrage and SMH at it’
    • ‘Right now I'm so ashamed of my home state, smh.’
    • ‘The sequels sucked so what makes them think a tv series will work! Smh.’
    • ‘SMH at the people who post videos on this site.’
    • ‘Wow smh, so many off-subject arguments and comments.’
    • ‘SMH at this nasty show.’
    • ‘That man is father of her children, and all she wants to do is embarrass him in front of them. SMH.’
    • ‘Smh @ her latest selfie.’
    • ‘You let the fake rumours influence your perception of him. SMH.’
    • ‘Smh. I'm going to need for her to know that she can't go around saying things like this.’
    • ‘It likes she does it for attention, smh.’

Origin

Early 21st century: sometimes also interpreted as short for so much hate.