Green’s Dictionary of Slang

fleek adj.

(US) smooth, admirable, thus adj. fleeky.

Urban Dict. 2 Oct. 🌐 That was a fleek move you pulled on that chic.
Section Boyz ‘Trapping Ain’t Dead’ 🎵 She's kinda peng / She’s kinda fleeky.
[US]Baltimore Sun (MD) 21 Apr. A15/4: Remember ‘fleek’? ‘Cash me outside’? Or regrettably, ‘Yas, Queen Yaasss’?

In phrases

on fleek (adj.)

(US campus) fashionable, top quality, thus v. fleek on, to be superlative.

[US]C. Eble (ed.) UNC-CH Campus Sl. Spring 2014 Fall 5: ON FLEEK — fresh, fashionable, attractive: ‘Her eyebrows were on fleek’.
[UK]Skepta ‘Lyrics’ 🎵 Lord of the Mics, you was spitting that heat / But right now, your bars ain’t on fleek.
Q. Vidal ‘Third Rail’ 🎵 Creepin’ in the night, fleekin’ on the mic.
Harlem Spartans ‘Money & Beef’ 🎵 Use two hands when I up that blam / Got one eye closed and my aim on fleek.
[UK]Central Cee ‘Day in the Life’ 🎵 Who's that with the hair on fleek? / She made me beep my horn, it’s peak.