The Collaborative International Dictionary of English v.0.48:

Vena \Ve"na\, n.; pl. Venae. [L. See Vein.]
   A vein.
   [1913 Webster]

   Vena cava; pl. Venae cavae. [L., literally, hollow vein.]
      (Anat.) Any one of the great systemic veins connected
      directly with the heart.

   Vena contracta. [L., literally, contracted vein.]
      (Hydraulics) The contracted portion of a liquid jet at and
      near the orifice from which it issues.

   Vena portae; pl. Venae portae. [L., literally, vein of
      the entrance.] (Anat.) The portal vein of the liver. See
      under Portal.
      [1913 Webster]

WordNet (r) 3.0 (2006):

vena cava
    n 1: either of two large veins that return oxygen-depleted blood
         to the right atrium of the heart