hal·lux / ˈhaləks/ • n. (pl. hal·lu·ces / ˈhal(y)əˌsēz/ ) Anat. a person's big toe. ∎ Zool. the innermost digit of the hind foot of vertebrates.

hallux
1. The ‘great toe’. On the pentadactyl hind limb, the digit on the tibial side, which is often shorter than the other digits.

2. The first digit of the foot of a bird, forming the hind toe in many species. In some (e.g. Coliidae) it is reversible, in others (e.g. Apodidae) it points forward, but in some species it is reduced or absent.

hallux (hal-ŭks) n. (pl. halluces) the big toe. h. rigidus painful stiffness and enlargement of the joint at the base of the big toe, resulting from osteoarthritis. h. valgus a deformity in which the big toe is displaced towards the other toes. It is associated with a bunion. h. varus displacement of the big toe away from the others.

hallux The innermost digit on the hindlimb of a tetrapod vertebrate. In humans it is the big toe and contains two phalanges. The hallux is absent in some mammals and in many birds it is directed backwards as an adaptation to perching. Compare pollex.