Meaning of acid

(adj) 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"; "a vitriolic critique"

being sour to the taste

having the characteristics of an acid; "an acid reaction"

(noun) 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

street name for lysergic acid diethylamide