What is 50th Base?
to go to 4th base with a different woman (or man) in all 50 states.
You:50! I finally did 50th base!
Partner: I thought this was fourth base!
You: it is for you, but not for me!
Having sex to the point where you are so sore you can't move, then forcing yourself on top of your partner and bouncing up and down.
1st guy: "Dude I got to 50th base last night"
2nd guy: "I thought I heard you two screaming, but I had no idea."
1st guy: "Yeah I can't feel my junk now."