Hydraulic definition1. When a quantity of water, oil, or other fluid is forced along one end of a line, it also forces against the other end of the line. Because these fluids (unlike a gas) cannot be compressed, when they are forced into a smaller cylinder they multiply the amount of force. Thus a driver can apply a small amount of force on the pedal or lever and a great amount of force is applied to the brake. Used in power steering , clutches , and brake systems .
2. When used as a verb, it means that oil or excessive gasoline has entered the combustion chamber so that when compression takes place, the fluid cannot be compressed. Something has to give and it is usually the connecting rod that bends. It is found in the expression, "the engine hydrauliced."