Watertight/ˈwɔːtərtaɪt/ Definition 1 of 3Pro Tip 1/3Physical Barrier Refers to actual objects that prevent water passage. Make sure the container is watertight before we submerge it. Pro Tip 2/3Emphasize Reliability Implies that something can be completely trusted not to fail. The watertight watch remained functional even after swimming. Pro Tip 3/3Literal Use Used to describe actual objects that contact water, like boats or containers. Your diving suit is watertight, ensuring you stay dry.