SGitR
Acronym for the Smartest Guy in the Room, short for Smartest Guy in the Room Syndrome. The Smartest Guy in the Room has an above-average IQ and knows it; he or she grew up being the smart kid. A SGitR is smart enough to know that s/he's smarter than most people, but not quite smart enough to recognize when s/he encounters other people who are smarter. S/he defaults to the belief that because s/he is smarter than the majority of the population, s/he must be smarter than the people s/he's talking to. When a SGitR is in a room full of smart people, s/he'll continue talking down to and/or correcting them, happily oblivious to the fact that s/he's now in an environment in which s/he is not, in fact, the smartest guy in the room. See also mansplaining, Dunning-Kruger Effect.
"Ugh, at the party I got cornered by this guy who would not stop correcting everything I said about axon growth and myelinization for long enough for me to explain that I wrote the paper he was misquoting."
"I know that guy... Andy. He does that all the time, he's a total SGitR."
"I know that guy... Andy. He does that all the time, he's a total SGitR."