Waterproof (adjective)

1. Not permitting the passage of water.
2. Designed or made to prevent water from entering.

Origin:

Water + proof, from middle english waterprove, from water + prove.

Examples:

1. His boots were waterproof and kept his feet dry.
2. The jacket has a waterproof and breathable membrane.
3. She put on a waterproof mascara before going out.
4. The tent is made of waterproof fabric.
5. The boat has a waterproof deck.