Vas \Vas\, n.; pl. {Vasa}. [L., a vessel. See {Vase}.] (Anat.) A vessel; a duct. [1913 Webster] {Vas deferens}; pl. {Vasa deferentia}. [L. vas vessel + deferens carrying down.] (Anat.) The excretory duct of a testicle; a spermatic duct. [1913 Webster]