The line on a female's legs that indicates how short her pants can be on any particular day, depending on how far up her leg she shaves.
Criz: Why didn't you wear those cute booty shorts today?
Justine: I couldn't, my shave line was too far down.
When a girl shaves just the top of her pubic hair so it doesn't show above her bikini bottom.
Girl 1: "Come on Skyrim! They're already at the beach!"
Girl 2: "Wait! I forgot to shave last night, I can't go!"
Girl 1: "Just do some tan line shaving!"
Girl 2: "Great idea!"