1. (Science: astronomy) The twelfth sign of the zodiac, marked <pisces/ in almanacs. A zodiacal constellation, including the first point of aries, which is the vernal equinoctial point; the fish.
2. (Science: zoology) The class of vertebrata that includes the fishes. The principal divisions are elasmobranchii, ganoidei, and teleostei.
Origin: L. Piscis a fish.