Green’s Dictionary of Slang

(US campus) semen.

1989		P. Munro Sl. U. 179: spoo sperm.
1995		in L. Burke (ed.) Routledge Lang. & Cult. Theory Reader 209: Most weaponry terms for the penis ring the changes on three types of weapon: guns (spoo gun, squirt gun, love pistol, passion rifle), spears or knives [...] and missiles [Simes:DLSS].