Definition of geek out
: to behave like a geek; especially : to become excited or enthusiastic about a favored subject or activity Rail buffs get to geek out aboard a 1924 Pullman-Standard Victorian Coach or a 1952 Granite Eagle, the latter a three-level dining car with a glass observation dome on the upper deck and a sunken lounge on the lower level. — The Wall Street Journal … fans will really geek out over the reproduced notepad that features Henson's original outlines and story ideas. Not that I did or anything. — Dalton Ross
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