Hydrolock (short for either hydraulic lock or hydrostatic lock) is a condition of an internal combustion engine in which an incompressible liquid has been introduced into its cylinder(s), resulting in the immobilization of the engine's pistons. The liquid causing this malfunction is often water, hence the prefix "hydro-". Hydrolock occurs in a 4-stroke engine when liquid is sucked into the engine's cylinder(s) during the intake stroke and, due to the incompressibility of the liquid, makes the compression stroke impossible. This, in turn, prevents the entire engine from turning, and can cause significant engine damage if one attempts to forcibly turn over or start the engine. Typically, connecting rods will be bent, making the engine uneconomical to repair. Confer flooded engine and vapor lock, two unrelated conditions which could easily be confused with hydrolock.