Green’s Dictionary of Slang

parking lot n.

[play on park v. (4)]

1. (US teen) the vagina.

[UK]Partridge DSUE (8th edn) 855: [...] since the latish 1960s.

2. (US campus) a place where men congregate.

[US]Eble Campus Sl. Mar. 7: veritable parking lot – any place where good looking guys (nice cars) congregate.