watertight - definition and synonyms

adjective 

Your browser doesn’t support HTML5 audio

/ˈwɔːtə(r)ˌtaɪt/
  1. 1
    a watertight container or room is made so that water cannot enter it
  2. 2
    something that is watertight such as an excuse, argument, case, or alibi is so good that no one can find anything wrong with it