Synonyms of watertight

Adjective

1. watertight, tight (vs. leaky)

usage: not allowing water to pass in or out

2. unassailable, unshakable, watertight, bulletproof, incontestable (vs. contestable), incontestible

usage: without flaws or loopholes; "an ironclad contract"; "a watertight alibi"; "a bulletproof argument"

Definition and meaning of watertight (Dictionary)