the game of throwing small objects, such as little balls of paper, inside a girls shirt with the goal of getting it to go in between her boobs.
Bryan: Look at Jessica over there. I'm going to play cleavageball! I'm gonna throw this paper ball inside her shirt.
Barney: You are going to miss! She doesn't have anything!
Barney: You are going to miss! She doesn't have anything!
by poloe December 07, 2012