(1):

(a.) 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.

(2):

(a.) Of or pertaining to that surface of a carpel, petal, etc., which faces toward the center of a flower.

(3):

(a.) Of or pertaining to the lower side or surface of a creeping moss or other low flowerless plant. Opposed to dorsal.