in-between, n.¹ — Green’s Dictionary of Slang

in-between n.¹

(Aus.) a male homosexual.

[1922		Broadway Brevities Aug. 32: Characters: Male / In-Between / Female].
1952		Lait & Mortimer USA Confidential 246: The excursion boat Admiral is popular for meeting girls, boys, and in-betweens.
1999		G. Seal Lingo 91: An in-between is a queen (male homosexual).
2002		Pete’s Aussie Sl. Home Page 🌐 in between: a queen.