The crossword solution for the term 'PEP UP, AS AN ENGINE' is 'SUPERCHARGE'. Supercharging is a process used to increase the power output of an engine by forcing more air into the combustion chamber. This is done by using a compressor, such as a supercharger or a turbocharger, to increase the pressure of the air-fuel mixture before it enters the engine. Supercharging can provide a significant boost in power and torque, allowing an engine to produce more power than it would normally be able to.