a crack, crevice, fissure, or hole which admits water or other fluid, or lets it escape; as, a leak in a roof; a leak in a boat; a leak in a gas pipe.-the entrance or escape of a fluid through a crack, fissure, or other aperture; as, the leak gained on the ship's pumps.-leaky.-to let water or other fluid in or out through a hole, crevice, etc.; as, the cask leaks; the roof leaks; the boat leaks.-to enter or escape, as a fluid, through a hole, crevice, etc. ; to pass gradually into, or out of, something; -- usually with in or out.