Waterproof means made so that water cannot get through. A waterproof jacket, waterproof to ten metres, keep it waterproof.
Water-resistant is a much weaker claim than waterproof, and the two are used loosely in advertising and precisely in standards. A waterproof coat that does not breathe leaves you wet from the inside, which is why the good ones cost what they do.
1adjectivewaterproofMade so that water cannot get through.
“Make sure your boots are waterproof before you go walking in the hills.”
waterproof is a quality of resistance.
Water plus -proof, from proof in the sense of able to resist, as in fireproof and bulletproof.
Proto-Indo-European
*wed-
Middle English
water
English
water
English, today
waterproof
From water + -proof. Compare West Frisian wetterproef (“waterproof”), Dutch waterproef (“waterproof”). water comes from Middle English water. From Middle English water, from Old English wæter (“water”), from Proto-West Germanic watar, from Proto-Germanic watōr (“water”), from Proto-Indo-European wódr̥ (“water”). 2
Etymology from Wiktionary, CC BY-SA