adj. 25B6; adjective
virulent herbicides : POISONOUS, toxic, venomous, noxious, deadly, lethal, fatal, mortal, dangerous, harmful, injurious, pernicious, damaging, destructive; poetic/literary deathly, nocuous.
a virulent epidemic : INFECTIOUS, infective, contagious, communicable, transmittable, transmissible, spreading, pestilential; informal catching.
a virulent attack on morals : VITRIOLIC, malicious, malevolent, hostile, spiteful, venomous, vicious, vindictive, bitter, rancorous, acrimonious, scathing, caustic, withering, nasty, savage, harsh.
harmless, amicable.