look up any word, like blumpkin:
 
1.
Ramming a girl with a pool cue then beating her father over the head with it.
"DUDE WTF, you went to 15th base with my sister last night and now my dads in the hospital!!!"
by Dillon Labrek August 16, 2006
 
2.
threesome with parents
Bob: "My gf caught me at 15th base last nite!"
Bobbalina: "That's awkward, what'd she do - turn it into sixteenth base?"
Bob: "17th"
by S1245 August 16, 2006