an air ball空心球
knee-high to a grasshopper
A: Hey, Nina. Fancy meeting you here. Do you come to the basketball court often?
B: Yeah, I try to shoot some hoops whenever I can. It's good exercise and gives me some me time out of the house.
A: Do you want to play some one-on-one?
B: Sure, but I'm warning you. I may whip your ass.
A: I don't think so. I've been playing since I was knee-high to a grasshopper. I can throw three-pointers in my sleep.
B: We'll see.
A: Okay, let's start.
B: Two points to me...and another two-pointer...and another. Haha! You threw an air ball.
A: Man, you're quick. And where did you learn to Slam-dunk like that?
B: My dad is the basketball coach at South Central Community College. I literally grew up on a basketball court.