Hand gesture used by motorcyclists and some others in respect and acknowledgment of fellow riders. An extended left hand wave with the arm slightly below the handlebar. This is done for both safety (don't wanna take your hands too far off the bars) and discreteness (it's an "inside thing".) Most riders are very friendly this way. Others won't return the gesture if you're riding a "foreign" bike or one not of the same make as theirs. Harley riders are notorious for this and other jackassery.

Another name for masturbation.

In sports, this is the act of slapping the behind of a teammate or competitor.

The act of grabbing a woman by the pussy

The same as a high-five but this one is done hands down way.

When two motorcyclists pass each other on the road and each lowers their hand in a symbol of friendship. They do not actually touch, but it is acknowledging each other's existance on motorcycles.

A symbol to notify something bad happening.