virulent

UK: /ˈvɪrjʊlənt/

US: /ˈvɪrjələnt, ˈvɪrə-/

US: (vir′yə lənt, vir′ə-)

WordReference Random House Learner's Dictionary of American English © 2025

vir•u•lent /ˈvɪryələnt, ˈvɪrə-/   adj. 

1. Pathology actively poisonous;
   very noxious;
   harmful or deadly;
   highly infective:
   a virulent strain of bacteria.
2. violently hostile;
   intensely bitter, hateful, or wishing evil:
   a virulent speech.

vir•u•lence, n. [uncountable]

WordReference Random House Unabridged Dictionary of American English © 2025

vir•u•lent  (vir′yə lənt, vir′ə-), adj. 

1. Pathology actively poisonous;
   intensely noxious:
   a virulent insect bite.
2. Medicine highly infective;
   malignant or deadly.
3. Microbiology [Bacteriol.] causing clinical symptoms.
4. violently or spitefully hostile.
5. intensely bitter, spiteful, or malicious:
   a virulent attack.

• Latin vīrulentus, equivalent. to vīr(us) poison (see virus) + -ulentus -ulent
• Middle English verulent 1350–1400

vir′u•lent•ly, adv. 
Synonyms

• 1. venomous.
• 5. vicious, acerbic.

Antonyms

• 1. harmless.

Collins Concise English Dictionary © HarperCollins Publishers::

virulent / ˈvɪrʊlənt/ adjective

1. (of a microorganism) extremely infective
2. (of a disease) having a rapid course and violent effect
3. extremely poisonous, injurious, etc
4. extremely bitter, hostile, etc

Etymology: 14th Century: from Latin vīrulentus full of poison, from vīrus poison; see virus

ˈvirulently adverb