Inflected forms: pl. baths (bthz, bäthz, bths, bäths) 1a. The act of soaking or cleansing the body, as in water or steam. b. The water used for cleansing the body. 2a. A bathtub. b. A bathroom. 3. A building equipped for bathing. 4. A resort providing therapeutic baths; a spa. Often used in the plural. 5a. A liquid in which something is dipped or soaked for processing: immersed the metal in an acid bath.b. A container holding such a liquid: emptied the bath of dye.6a. A medium, such as oil or sand, that controls the temperature of objects placed in it. b. A container holding such a medium.