Source : Webster's Revised Unabridged Dictionary (1913)

Acerb \A*cerb"\, a. [L. acerbus, fr. acer sharp: cf. F. acerbe.
   See {Acrid}.]
   Sour, bitter, and harsh to the taste, as unripe fruit; sharp
   and harsh.

Source : WordNet®

acerb
     adj 1: sour or bitter in taste [syn: {acerbic}, {astringent}, {sharp}]
     2: harsh or corrosive in tone; "an acerbic tone piercing
        otherwise flowery prose"; "a barrage of acid comments";
        "her acrid remarks make her many enemies"; "bitter words";
        "blistering criticism"; "caustic jokes about political
        assassination, talk-show hosts and medical ethics"; "a
        sulfurous denunciation" [syn: {acerbic}, {acid}, {acrid},
        {bitter}, {blistering}, {caustic}, {sulfurous}, {sulphurous},
         {venomous}, {virulent}, {vitriolic}]