Vas \Vas\, n.; pl. Vasa. [L., a vessel. See Vase.]

(Anat.) A vessel; a duct.

Vas deferens; pl. Vasa deferentia. [L. vas vessel + deferens carrying down.]

(Anat.) The excretory duct of a testicle; a spermatic duct.

Source: Webster's Revised Unabridged Dictionary (1913)