Slang A highly intelligent person: "These companies are not hot Silicon Valley startups swarming with Gen-X brainiacs” ( Ronald Henkoff). (noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "brainiac" in a sentence
"This brainiac is driving with his left foot extended out the driver’s side window and is resting his ankle on the side mirror."
"Milligan will play Ethan, who the NYPost not only describes as a brainiac, but also as someone who possesses other qualities valued in the 90210."
"Though it would please me to think marrying outside my ethnic group has afforded my spawn a clearer shot at intellectual greatness, any mad 'brainiac' DNA my children might possess more likely arrives via their crazy, drunken, Mensa-smart goyishe grandfather than from their closest Ashkenazi kin."