Spir'a-cle, n.

(spir'a-kl, or spir'a-kl, 89) (Synop., § 130), n. [Lat. spiraculum, from spirare, to breathe; Fr. spiracule, It. spiracolo, spiraglio, Sp. espiraculo, Pr. espiroth.]

1. (Anat.) A small aperture in animal and vegetable bodies, by which air or other fluid is exhaled or inhaled.
2. (Entom.) The external aperture of the trachea or air tube of an insect. It is a round or narrow opening on the surface of the body, usually surrounded by a horny ring, fringed with short hairs, and capable of being closed. Such openings are very various in number and position, but are usually situated between the segments of the body.
3. Any small aperture, hole, or vent.