[1] : The Collaborative International Dictionary of English v.0.48

water-tight \wa"ter-tight`\, a.
   so tight as to retain, or not to admit, water; not leaky.
   1913 webster

[2] : WordNet (r) 2.0

watertight
     adj 1: having no leaks syn: leakproof
     2: not allowing water to pass in or out
     3: without flaws or loopholes; "an ironclad contract"; "a
        watertight alibi"; "a bulletproof argument" syn: ironclad,
         unassailable, unshakable, bulletproof
see also:
leakproof ironclad unassailable unshakable bulletproof 

[3] : Moby Thesaurus II by Grady Ward, 1.0

64 moby thesaurus words for "watertight":
   airtight, ballproof, bold, bombproof, bulletproof, burglarproof,
   close, compact, corrosionproof, dampproof, dripproof, dustproof,
   dusttight, fast, fire-resisting, fireproof, firm, fit for sea,
   flameproof, floodproof, foolproof, gasproof, gastight, hermetic,
   hermetically sealed, holeproof, impervious to, leakproof,
   lightproof, lighttight, moistureproof, noiseproof, oilproof,
   oiltight, proof, proof against, punctureproof, rainproof,
   raintight, resistant, rustproof, sea-kindly, sealed, seaworthy,
   seepproof, shatterproof, shellproof, shut fast, smokeproof,
   smoketight, snug, soundproof, staunch, stiff, stormproof,
   stormtight, tender, tight, water-repellant, waterproof, weatherly,
   weatherproof, windproof, windtight

Watertight >> W Words
Watertight, definition of term: Watertight
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