1. To strike something with one or more quick, light blows, as when getting someone's attention; to knock or tap at something swiftly and lightly. I thought I heard someone rapping at my window in the middle of the night, so I was wide awake with fear until morning! The wind was causing a tree branch to rap at the door in a most unsettling manner.

2. To utter spoken word rhymes meant to mock or denigrate another person during a rap battle. You've got to have thick skin when someone's rapping at you, but you also have to know that it's all just part of the game.