waterproof pants

noun[plural only]2

1. •
   Pants that are waterproof, such as rainpants or snow pants.
2. •
   Synonym of plastic pants (“an undergarment worn over a diaper/nappy (or underwear) to prevent leakage.”).

   • Waterproof pants are helpful as the baby gets older, since they prevent wetting of outer clothes, nightgowns, etc. — 1979