# watertight

/ˈwɔtɝˌtaɪt/ (US) · /wˈɔːtətˌaɪt/ (UK)

Source: https://englishreference.com/word/watertight
Updated: 2026-08-27

## Senses

### 1. keeping water out

adjective · CEFR B2

made so tightly that water cannot get in or out.

For teachers: constructed or sealed so tightly as to be impermeable to water.

- Make sure the container is watertight before you put it in your bag.
- The engineers tested the hull to ensure it was completely watertight before the submarine's first deep-sea mission.

### 2. perfect or certain

adjective · CEFR C1 · Formal

so well planned or explained that no one can find a mistake or defeat it.

For teachers: impossible to defeat, evade, or nullify; used of arguments, plans, or legal cases.

- The police had a watertight case against the thief.
- The legal team spent months building a watertight argument to ensure the contract could not be challenged in court.

Usage: Often collocates with 'case', 'argument', 'alibi', or 'excuse'.

## Examples

- The new tent is completely watertight.
- The lawyer presented a watertight defense that left the jury with no questions about the client's innocence.
- While the physical seals on the container were watertight, the logical gaps in the company's financial report made the entire proposal vulnerable to scrutiny.

---

From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.