1) Bright 2) Bright as a button 3) Cerebral 4) Clever 5) Intellectual 6) Intelligent 7) Sharp 8) Sharp as at ack 9) Smart as a whip 1) Bright 2) Brilliant 3) Cerebral 4) Clever 5) Eggheaded 6) Exclusively Saxon word 7) Exclusively Anglo word 8) Fit for Mensa 9) Intellectual 10) Intellectually gifted 11) Intelligent 12) Like a certain trust 13) Like an egghead 14) Like Mensa members 15) Like the valedictorian 16) Mensa material 17) Opposite of dense 
• (a.) Having an active or vigorous mind.
Brain'y adjective Having an active or vigorous mind. [ Colloq.]
[adj] - having or marked by unusual and impressive intelligence
brilliant adjective having or marked by unusual and impressive intelligence; `some men dislike brainy women`; `a brilliant mind`; `a brilliant solution to the problem`
intelligent; clever; intellectual.