Green’s Dictionary of Slang

egghead adj.

also egg-heady

(orig. US) intellectual, or pretentiously so.

[US]N.Y. Times 19 Oct. E1: Writers of letters to editors tend to be in the intellectual or ‘egghead’ category.
[US]J. Steinbeck Sweet Thursday (1955) 17: You’re nice, Doc, nice and egg-heady, but a guy would have to be nuts to think you was smart.
[US]Mad mag. July 28: The exciting new egghead tome, ‘The best of Dondi’.
[US]K. Marlowe Mr Madam (1967) 245: Not dirty titles, heavens! Just Best Sellers, with egghead names.
[US](con. 1950s) H. Junker ‘The Fifties’ in Eisen Age of Rock 2 (1970) 100: Alienation was the absurd egghead bit.
[US]L. Rosten Dear ‘Herm’ 149: This [...] had nothing to do with ‘egg-head’ palaver about Freedom for Civillians.
[SA]S. Motjuwadi ‘What is not White is Darkie’ in Mutloatse Forced Landing 187: I am with a group of egghead buddies at our favourite Kliptown joint.
[US]S. Morgan Homeboy 165: Copping egghead comments to drop at the upcoming San Francisco Film Festival.