-adjective

 acid in temper, mood, or tone (acerbic commentary) (an acerbic reviewer)

-adjective

 caustic, biting, or rancorous especially in feeling, language, or manner (an acrimonious dispute)

-adjective

1 : causing contraction of soft organic tissues : styptic, puckery (astringent lotions) (an astringent fruit)
2 : suggestive of an astringent effect upon tissue : rigidly severe : austere (dry astringent comments); also: pungent, caustic

-verb

1 : to excite bitter feelings in (embittered by divorce)
2 : to make bitter

-adjective

1 : acid-forming
2 : acid

-adjective

1 : marked by an often ill-natured inclination to stress faults and raise objections (captious critics)
2 : calculated to confuse, entrap, or entangle in argument (a captious question)

-noun

1 a : a sulfate of any of various metals (as copper, iron, or zinc); especially : a glassy hydrate of such a sulfate b : oil of vitriol
2 : something felt to resemble vitriol especially in caustic quality; especially : virulence of feeling or of speech

-adjective

1 : capable of destroying or eating away by chemical action : corrosive
2 : marked by incisive sarcasm
3 : relating to or being the surface or curve of a caustic

-noun

1 : a caustic agent: as a : a substance that burns or destroys organic tissue by chemical action b :sodium hydroxide 
2 : the envelope of rays emanating from a point and reflected or refracted by a curved surface

-noun

bitter deep-seated ill will, enmity

-adjective

1 : having a rank smell or taste
2 : offensive