A street elbow is a type of plumbing or piping fitting intended to join a piece of pipe and another fitting at an angle. The difference between a street elbow and a regular elbow is the gender of its two connections.
A regular elbow has a hub or female-threaded connection on each end, so it can join two male pipes. Instead, a street elbow has a female fitting on one end and a male fitting on the other. The advantage of the street elbow is that it can be connected directly to another fitting without having to use an additional short connecting piece.