constructed or fitted so tightly as to be impervious to water: The ship had six watertight compartments.
so devised or planned as to be impossible to defeat, evade, or nullify: a watertight contract; a watertight alibi.
Origin of watertight
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for watertightness
Historical Examples of watertightness
Again the work has to be done uniformly well, not only for appearance sake but because of the necessity of watertightness.
Exceptionally good concreting is essential in tank work if watertightness is to be secured.
not permitting the passage of water either in or outa watertight boat
without loopholesa watertight argument
kept separate from other subjects or influencesdifferent disciplines are often thought of in watertight compartments
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Online Etymology Dictionary, © 2010 Douglas Harper