virulent

adjective

1 some plant varieties can withstand being sprayed by the most virulent herbicides:

poisonous, toxic, venomous, noxious, deadly, lethal, fatal, mortal, terminal, death-dealing, life-threatening, dangerous, harmful, injurious, pernicious, damaging, destructive, unsafe;

contaminating, polluting;

literary deathly, nocuous, mephitic;

archaic baneful.

▷antonyms non-toxic, harmless, safe.

2 a virulent epidemic of cholera swept through London:

highly infectious, highly infective, highly contagious, infectious, infective, contagious, rapidly spreading, communicable, transmittable, transmissible, spreading, malignant, uncontrollable, pernicious, pestilential;

severe, extreme, violent, dangerous, harmful, lethal, life-threatening;

informal catching;

literary pestiferous.

▷antonyms non-contagious.

3 a virulent attack on contemporary morals:

vitriolic, malicious, malevolent, malignant, malign, evil-intentioned, resentful, hostile, spiteful, venomous, vicious, vindictive, bitter, rancorous, acrimonious, mordant, astringent, incisive, cutting, biting, scathing, caustic, stinging, blistering, searing, withering, abusive, mean, nasty, aggressive, savage, harsh, devastating;

informal bitchy, catty;

literary malefic, maleficent.

▷antonyms amicable, benevolent.

virulent Oxford Dictionary of English