acid vs virulent

acid is a noun but virulent is not a noun.

Word	Noun	Adjective	Verb	Adverb
acid	Yes	Yes	No	No
virulent	No	Yes	No	No

As adjectives, acid and virulent are synonyms defined as:

Other synonyms of acid include acerb, acerbic, acrid, bitter, blistering, caustic, sulfurous, sulphurous, vitriolic.

acid (noun)	virulent (noun)
street name for lysergic acid diethylamide
any of various water-soluble compounds having a sour taste and capable of turning litmus red and reacting with a base to form a salt

acid (adjective)	virulent (adjective)
having the characteristics of an acid	infectious; having the ability to cause disease
being sour to the taste	extremely poisonous or injurious; producing venom
harsh or corrosive in tone	harsh or corrosive in tone