The phrase "leak proof" is commonly used to describe a product or container that is designed to prevent leakage of its contents. There are several synonyms that can be used in place of this phrase, including "waterproof," "airtight," and "sealed." "Waterproof" implies that the product or container is impervious to water and will not allow any liquid to escape. "Airtight" suggests that the container or product is tightly sealed to prevent air from escaping or entering. "Sealed" simply refers to a container that has been securely closed to prevent any contents from spilling out. Other synonyms for "leak proof" include "tight-fitting," "hermetically sealed," and "self-sealing".