proof against penetration or permeation by water; impervious to water; as, a waterproof garment; a waterproof roof.-a substance or preparation for rendering cloth, leather, etc., impervious to water.-cloth made waterproof, or any article made of such cloth, or of other waterproof material, as rubber; esp., an outer garment made of such material.-to render impervious to water, as cloth, leather, etc.