| 1. | impervious to water. |
| 2. | rendered impervious to water by some special process, as coating or treating with rubber: a waterproof hat. |
| 3. | Chiefly British. a raincoat or other outer coat impervious to water. |
| 4. | any of several coated or rubberized fabrics that are impervious to water. |
| 5. | to make waterproof. |