Green’s Dictionary of Slang

(US gay/campus) of a man (whether actually homosexual or not), to look exaggeratedly ‘feminine’ in dress and style; thus flaming n., acting in an obviously homosexual manner.

1972		B. Rodgers Queens’ Vernacular 82: flame [it up] to overemphasize, often deliberately, all girlish traits attributed to the effeminate.
1989		P. Munro Sl. U.
1992		Eble Campus Sl. Apr. 4: flame – display homosexuality in a particularly flamboyant fashion.
2021		J. Ellroy Widespread Panic 14: A flit flamed by and ogled my piece.