The Low Five 

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.

Tom was driving his Harley down the road when he saw Jim comming the other way on his crotch rocket. Both riders lowered their left hands and gave the low five.

The Low Five by masterfw July 2, 2009

high-five to the low-two 

A kick to the nuts. Refers to the five toes of the kicker's foot rising up to mash the two testicles of the recipient's ball-bag.

When my boss called me into the office to review my job performance, she said that if I'd spent more time working than reading Urban Dictionary, I'd still have a job on Monday. It was a real high-five to the low-two.

high-five to the low-two by TerribleDH March 20, 2011