A rocket engine that produces thrust using only one propellant. This is typically achieved either through the propellant's exothermic decomposition over a catalyst or through simply exhausting the propellant from a high pressure tank into a lower pressure environment (cold-gas thrusters).
Cervone, Angelo, Lucio Torre, Luca d'Agostino, Antony J. Musker, Graham T. Roberts, Cristina Bramanti, and Giorgio Saccoccia. "Development of hydrogen peroxide monopropellant rockets." In 42nd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, p. 5239. 2006.