Definition of harmful in US English:

harmful

adjective

  • Causing or likely to cause harm.

    ‘sugars that can be harmful to the teeth’
    ‘shield the planet from harmful cosmic rays’
    • ‘High work demands and high mobilisation of efforts at work may not always indicate harmful stress.’
    • ‘It is the acidic environment produced by the harmful bugs that results in tooth decay.’
    • ‘My mother was so protective that now I feel it was actually quite harmful to me.’
    • ‘Chocolate is legal and more effective and also has no harmful side-effects whatsoever.’
    • ‘We learn patterns of behaviour there - some of which are useful, some of which are harmful.’
    • ‘It is not unusual to find substances in illegal drugs that are much more harmful than the drugs themselves.’
    • ‘More drugs fail clinical tests because of harmful effects on the liver than for any other reason.’
    • ‘This is a highly controversial treatment and it is suggested that it might be harmful.’
    • ‘Are the more sexual representations merely offensive, or can they be genuinely harmful?’
    • ‘Pollution on our roads is far more harmful to us all than cigarette smoke will ever be.’
    • ‘It could be said that alcohol and tobacco are much more harmful drugs than either cocaine or heroin.’
    • ‘Not all these chemicals are healthy, not all are harmful, most can be either.’
    • ‘There are alternative fuels, some less harmful to the atmosphere and some which do no harm at all.’
    • ‘The lack of atmosphere also means there's no protection from harmful radiation in the solar wind.’
    • ‘From what I've been told smoking cannabis is allegedly less harmful than cigarettes.’
    • ‘To restrict fluid to the extent of causing dehydration may even be harmful.’
    • ‘The Thames has highly dangerous levels of e.coli and other harmful bacteria.’
    • ‘The lining of the stomach produces a B acid to help digest food and also protect from harmful bacteria.’
    • ‘It is quite a harmful chemical and may produce adverse reactions.’
    • ‘CFC gas damages the ozone layer which protects the earth from harmful rays from the sun.’
    damaging, injurious, detrimental, dangerous, deleterious, unfavourable, negative, disadvantageous, unhealthy, unwholesome, hurtful, baleful, wounding, destructive, environmentally unfriendly
    View synonyms

Pronunciation

harmful

/ˈhärmfəl//ˈhɑrmfəl/