tennis ball tits

A person (usually a woman) who has small boobs. But, the boobs are near-perfect spheres.

John: Dude check out that girl over there!
Gabe: Yeah dude, her boobs are perfectly baseball shaped! Small, but yet very round and curve perfectly!
John: Yeah, they’re almost like tennis balls.
Gabe: So THAT’S why she called “tennis ball tits”?