Slapping palms as a form of greeting a friend and then holding their hand as you pull your fingers back until it makes a snapping sound.

When a reply to a tweet gets more likes than the tweet it was replying to, usually indicating the unpopularity or stupidity of the original tweet

digital authentication protocol

a greeting mechanism that can consist of or combine multiple methods of hand based interaction (e.g. handshake/fistbump)

The knocking of fists together as a greeting, or form of respect

The knocking of fists together as a greeting, or form of respect.

If one person's ass is penetrated by two objects, it is generically called double anal penetration (sometimes abbreviated dp).

Double-Double: Multiple penetration by four penises. Two penises in the mouth and anus simultaneously.

Triple-Double: Multiple penetration by six penises. Two penises in the mouth, vagina, and anus simultaneously.