harmful

harmful adjective afflicting, bad, baleful, baneful, calamitous, cataclysmic, catastrophic, consuming, corrosive, costly, crippling, cruel, crushing, dangerous, deleterious, destructive, detracting, detrimental, devouring, dire, disadvantageous, disastrous, disserviceable, evil, fell, fiendish, foul, hurtful, inexpedient, infectious, injurious, insalubrious, internecine, malefic, maleficent, malicious, malign, mephitic, merciless, miasmal, mischievous, morbific, nasty, nocent, nocuous, noisome, noxious, noxius, pestiferous, pestilential, pitiless, poisonous, polluted, ruinous, spiteful, subversionary, subversive, toxic, treacherous, troublous, unfavorable, unfortunate, unhealthy, unlucky, unpropitious, unsafe, unwholesome, venomous, vicious, wicked, wounding
Associated concepts: harmful consequences from an overt act, harmful products

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See also: adverse, dangerous, deleterious, destructive, detrimental, disadvantageous, disastrous, fatal, hostile, inadvisable, incendiary, inimical, insalubrious, invidious, lethal, malevolent, malicious, malignant, negative, noxious, oppressive, outrageous, painful, peccant, pernicious, pestilent, prejudicial, scathing, sinister, toxic, virulent