The Collaborative International Dictionary of English v.0.48:
Seta \Se"ta\ (s[=e]"t[.a]), n.; pl. Setae (s[=e]"t[=e]). [L.
seta, saeta, a bristle.]
1. (Biol.) Any slender, more or less rigid, bristlelike organ
or part; as the hairs of a caterpillar, the slender spines
of a crustacean, the hairlike processes of a protozoan,
the bristles or stiff hairs on the leaves of some plants,
or the pedicel of the capsule of a moss.
(a) One of the movable chitinous spines or hooks of an
annelid. They usually arise in clusters from muscular
capsules, and are used in locomotion and for defense.
They are very diverse in form.
(b) One of the spinelike feathers at the base of the bill
of certain birds.