based, adj. — Green’s Dictionary of Slang

based adj.

[originated in online right-wing politics, which adopted it during the Gamergate controversy over female video game reviewers. The origins lie either in SE based in fact, used to denote one’s ‘anti-woke’ stance or in basehead under base n.¹ in which the smoker's style, seen as abonormal or eccentric, was recast by the raper Lil B as swagger and fearless self-belief]

used to indicate agreement with an idea or statement or admiration of an individual or their action; however it is equally found in ironic use and the intended meaning can be hard to discern.

2007		Lil B [album title] Based Boys .
2011		Lil B ‘Where Dem Based Boys’ 🎵 Where them based boys, where them, / where them, based boys .
2011		Urban Dict. 27 Jan. 🌐 Lil B [...] Calls himself ‘based god’ which also gives people an excuse to like his shitty fuckery that they call rap.
2018		dictionary-com 6 Sept. 🌐 Based is a slang term that originally meant to be addicted to crack cocaine (or acting like you were), but was reclaimed by rapper Lil B for being yourself and not caring what others think of you—to carry yourself with swagger.
2020		Urban Dict. 26 Nov. 🌐 based A word used when you agree with something; or when you want to recognize someone for being themselves,.
2023		Twitter 2 Sept. 🌐 [of Ukrainian drone operators checking targeting co-ordinates by calling the target] Extremely based beyond belief.