Source : Webster's Revised Unabridged Dictionary (1913)

Brainy \Brain"y\, a.
   Having an active or vigorous mind. [Colloq.]

Source : WordNet®

brainy
     adj : having or marked by unusual and impressive intelligence;
           "some men dislike brainy women"; "a brilliant mind"; "a
           brilliant solution to the problem" [syn: {brilliant}, {smart
           as a whip}]
     [also: {brainiest}, {brainier}]