What does watertight mean?
Watertight is an adjective describing something that is completely sealed against water, such as a boat compartment, pipe, case, or container. Its literal sense implies more than ordinary resistance to moisture: the object permits no passage of water. By extension, people use watertight for arguments, explanations, plans, or security arrangements that are so complete and carefully supported that they leave no significant gaps for criticism. In this figurative use, the word is close to airtight and implies unusually rigorous reasoning rather than merely a convincing case. The expression is used in both British and American English. Watertight can also describe something so tightly fitted or constructed that little or no light, air, or other material can pass through. Its strength makes it useful for describing demanding standards of waterproofing, precision, and reliability, though it can sound overly absolute in less formal conversation.
adjectiveImpervious to water or completely sealed against water. Figuratively, watertight means so carefully constructed or reasoned that it leaves no room for criticism or doubt.
- Impervious to water or completely sealed against water.
- So tightly constructed that it admits no light, air, or other material.
- Figuratively, logically precise and beyond effective criticism.
"The engineers checked every hatch until the submarine's compartments were watertight."
"The engineers checked every hatch until the submarine's compartments were watertight."
"Her explanation of the discrepancy was watertight, leaving no room for doubt."
A watertight argument leaves its critics with nothing to squeeze through.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of watertight
Watertight is an English compound formed from water and tight, a productive pattern used to describe a substance's resistance to a particular substance. The compound emerged in the 19th century, especially in descriptions of vessels and their compartments. Its figurative sense developed from the idea of an enclosure that admits no flaw or counterargument. Related English formations include waterproof and waterless, while airtight expresses the parallel idea of excluding air.
Related word forms
How watertight is actually used
The word is formal but widely used in technical, journalistic, and argumentative contexts. In figurative use, it conveys stronger certainty than merely well-supported or persuasive and can sound emphatic or absolute.
Easily confused with watertight
A watertight enclosure prevents the passage of water, whereas an airtight enclosure prevents the passage of air; figuratively, the two words are often interchangeable when describing a flawless argument or plan.