The Collaborative International Dictionary of English v.0.48:

Ventral \Ven"tral\, a. [L. ventralis, fr. venter the belly;
   perhaps akin to G. wanst: cf. F. ventral.]
   1. (Anat.) Of, pertaining to, or situated near, the belly, or
      ventral side, of an animal or of one of its parts; hemal;
      abdominal; as, the ventral fin of a fish; the ventral root
      of a spinal nerve; -- opposed to dorsal.
      [1913 Webster]

   2. (Bot.)
      (a) Of or pertaining to that surface of a carpel, petal,
          etc., which faces toward the center of a flower.
      (b) Of or pertaining to the lower side or surface of a
          creeping moss or other low flowerless plant. Opposed
          to dorsal.
          [1913 Webster]

   Ventral fins (Zool.), the posterior pair of fins of a fish.
      They are often situated beneath the belly, but sometimes
      beneath the throat.

   Ventral segment. (Acoustics) See Loop, n., 5.
      [1913 Webster]