Answer: waterproof

AnswerCrossword Clue
WATERPROOFImpervious to rain
WATERPROOFWhat Wellingtons should be
WATERPROOFBritish raincoat
WATERPROOFImpervious to H2O
waterproofImpervious to water
waterproofproof against water / to make waterproof
waterproofNot liable to be washed away by water