1. Unequal length in corresponding fingers or toes; especially, referring to birds with three toes forward and one backward.

This is common with songbirds and other perching birds, as well as hunting birds; such as, eagles, hawks, and falcons.
2. Possessing corresponding digits of unequal length on either side of the body.
3. Having unequal toes.
4. A group of herbivorous mammals characterized by having the hoofs in a single series around the foot; such as, the elephant, rhinoceros, etc.