Jim: Hey, what happened to your elbow? It's all bandaged up.
Tony: Well, I was riding my bike to school yesterday and I ate it when I was going down hill.
Jim: Wow! You have to be careful.
Susie: I heard your boyfriend is teaching you how to skateboard.
Jenny: Yeah, that's right.
Susie: Is it hard?
Jenny: Well, the first few days I was trying to figure out how to keep my balance. I ate it a lot and scrapped up my knees and hands.
Meaning: "to eat it" is an idiom that means "to fall" while doing some kind of sport or activity (surfing, snowboarding, riding a bike, jogging, etc.) Usually it is used when a person falls down and gets a little hurt.