Green’s Dictionary of Slang

y-bone steak n.

[the fork of the thighs + play on SE T-bone steak]

the female genitals.

R. Daltry in Who In Their Own Words cited at www.siouxcitysue.com 🌐 There’s something about a Y-bone steak I can’t resist.
Roger’s Profanisaurus - The Magna Farta 473/2: Y bone steak n. Female opposite of a tube steak.