A Working Perpetual Motion Machine (abbreviated as WPMM, obviously) is a concept invented by Trotto Frekkensnork. It describes a perpetual motion machine that does not violate the laws of physics.
Frekkensnork achieves this by saying that a perpetual motion machine will not function in our Universe, but might work in a Universe that has different laws of physics.
Therefore, a working perpetual motion machine is a machine that, apart from itself, should also have a Universe with suitable laws of physics.