A flange is an external or internal rib, or rim, for strength, as the flange of an iron beam; or for a guide, as the flange of a train wheel; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc.

Alternatively, a flange can be a plate or ring to form a rim at the end of a pipe when fastened to the pipe. A blind flange is a plate for covering or closing the end of a pipe. A flange joint is a joint, as that of pipes, where the connecting pieces have flanges by which the parts are bolted together.

A flange rail is a rail with a flange on one side, to keep wheels, etc. from running off.

Prov Room

9A Flange

Flange turning is the process of forming a flange on a wrought iron plate by bending and hammering it while hot.

Flange is also a slang term for female genitalia in parts of the UK and Ireland.

The phrase "a flange of baboons" is also occasionally used as a way of referring to a baboon troop [1]. 

This usage is derived from a sketch about the talking gorilla Gerald in the British TV comedy series, Not The Nine O'clock News.