Water can't penetrate something that's waterproof. Umbrellas and rain boots don't work very well if they're not waterproof.

Waterproof jackets will keep you dry even if it starts to rain, and waterproof mascara won't run in black streaks down your face even if you're weeping at a sad movie. You can use this word as a verb, too: "We should waterproof the tent before we go camping this weekend — it's supposed to pour!" If you're British, you might also use waterproof as a noun, to mean a waterproof rain coat.

Definitions of waterproof
  1. adjective
    not permitting the passage of water
    synonyms: rainproof, waterproofed
    of such close construction as to be impermeable
  2. verb
    make watertight
    Waterproof the coat”
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    type of:
    seal, seal off
    make tight; secure against leakage
  3. noun
    any fabric impervious to water
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    type of:
    cloth, fabric, material, textile
    artifact made by weaving or felting or knitting or crocheting natural or synthetic fibers
  4. noun
    a water-resistant coat
    synonyms: raincoat
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    show 4 types...
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    a lightweight belted raincoat typically made of tan gabardine with a distinctive tartan lining; named for the original manufacturer
    mac, macintosh, mack, mackintosh
    a waterproof raincoat made of rubberized fabric
    trench coat
    a military style raincoat; belted with deep pockets
    oilskin, slicker
    a macintosh made from cotton fabric treated with oil and pigment to make it waterproof
    type of:
    an outer garment that has sleeves and covers the body from shoulder down; worn outdoors
Word Family

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