An emulator is one of the three period 4 oscillators that produce sparks similar to those produced by a lightweight spaceship, middleweight spaceship, or heavyweight spaceship. They are the lightweight emulator, middleweight emulator, and heavyweight emulator respectively. It is possible to construct larger emulators, but they require stabilizing objects to suppress their non-sparks and so are of little use (except for the overweight T-nose. The three standard emulators were discovered by Robert Wainwright in June 1980. All of the P4 oscillators can eat gliders.
In general, emulator can refer to any oscillator that produces middleweight or heavyweight sparks, e.g. 258P3, the P4 heavyweight volcano shown under heavyweight emulator, the middleweight volcano or Snacker 2.