Clutch: A friction type of uncoupling device used to disengage an engine from the transmission during shifting. Clutches are normally linked to a clutch pedal in the driver's compartment so that the driver can control clutch operation. When a driver pushes down on the clutch pedal, a linkage forces a plate to move. This movement releases the engagement pressure from the friction disks. When the pressure is released from the clutch plate, the power flow is interrupted and the engine runs without transmitting any power to the power train.