Green’s Dictionary of Slang

three-wheeled trike n.

a lesbian.

1999		Roger’s Profanisaurus 3 in Viz 98 Oct. 15: gap-lapper n. A three-wheeled trike. Or possibly one who runs circuits around a jumper shop.
2003		B. Dark Dirty Cockney Rhy. Sl. 98: The problem with the women in athletics is that they may look nice but they’re all three wheelers.