When two people hit their knuckles together (when hands are in a fist). Many times used instead of a handshake or high-five.

To beat the shit out of someone or something using your bare hands

1) fight
2) step up

To hit a person with your knuckles.

Short for brass knuckles.

A synonym to pound it. It is a fist to fist contact in a congratulatory way. Often used to replace a high 5 or shaking hands.

A hand gesture characterized by an individual forming a closed fist with one hand and extending the index finger to the proximal interphalangeal joint only. The joint should be flexed so the distal phalange points inward toward the palm.

The gesture is executed when two participants each form this fist and lightly tap their PIP joints together.

Often initiated by one person doing or saying something really cool and the other person recognizing and respecting that action by holding up their fist as described above and saying "knuck".