Definition of power level:
(n) :
(fandom slang, especially Japanese fiction) A symbolic and often arbitrary unit of measurement representing strength and fighting ability.
(n) :
(by extension, Internet slang) An interest or specialized knowledge in a subject seen as uncool, especially related to video games and otaku culture.
(n) :
(by extension, Internet slang, alt-right) Extreme political views, especially those on the far right.
(n) :
Used other than figuratively or idiomatically: see power, level.