Expiration, n.
Etymology: [L. expiratio,exspiratio: cf. F. expiration. See Expire.]
1. The act of expiring; as: (a)(Physiol.)
The act or process of breathing out, or forcing air from the lungs through the nose or mouth; as, respiration consists of inspiration and expiration; -- opposed to Ant: inspiration. (b) Emission of volatile matter; exhalation. The true cause of cold is an expiration from the globe of the earth. Bacon.
(c) The last emission of breath; death. "The groan of expiration." Rambler. (d) A coming to a close; cessation; extinction; termination; end. Before the expiration of thy time. Shak.
2. That which is expired; matter breathed forth; that which is produced by breathing out, as a sound. The aspirate "he," which is . . . a gentle expiration. G. Sharp.
Shades of meaning
Fernald has no entry of its own for expiration; he lists it under end.
Where he writes about it:
Expiration signifies the coming to an end in the natural course of things; as, the expiration of a year, or of a lease; it is used of things of some consequence; we do not ordinarily speak of the expiration of an hour or of a day. — from end