Dictionary.com
Thesaurus.com

brainiac

American  
[brey-nee-ak] / ˈbreɪ niˌæk /

noun

  1. a highly intelligent person.


brainiac British  
/ ˈbreɪnɪˌæk /

noun

  1. informal a highly intelligent person

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of brainiac

From Brainiac, a superintelligent, villainous alien in the Superman comics, probably brain + (man)iac

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Living up to his reputation as Cahiers’ brainiac bad boy, he pockets the office’s petty cash to road-trip to the Cannes premiere of Truffaut’s “The 400 Blows.”

From Los Angeles Times

The second characteristic is that these evildoers are brainiacs, they're incredibly intelligent.

From Salon

OK brainiac, but how do you know the right way to prepare this photon to get it to carry as much information as possible about the thing you want to measure?

From Salon

Revolori's amiable turn as the band's well-read brainiac keeps a group that primarily depends on edged weapons and acrobatics connected to its large-heartedness.

From Salon

Holmes literally modeled her look and demeanor after Steve Jobs, which was such a weird thing to do that it only reinforced her image as a quirky brainiac.

From Salon