Generally, this term is used by those who need to release urine. The symbolism of "long horse" and "shortwalk" are up to the user's interpretation.
John: You know, though our conversation is enthralling, I admit I must taking the long horse for a short walk. In other words, I must urinate, as you may know from the saying's entry on Urban Dictionary.
Jane: Ok.
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.
A sunburn or suntan focused on the left arm. It is caused by the left side of the body being the only half that gets exposed to sunlight while driving. Presumably, it would be located on the right side of the body in countries where they drive on the left side of the road.
I had a trucker's tan after driving for 10 straight hours on a sunny day.