1. To breathe out; to emit from the lungs; to throw out from the mouth or nostrils in the process of respiration; -- opposed to inspire. Anatomy exhibits the lungs in a continual motion of inspiring and expiring air. Harvey. This chafed the boar; his nostrils flames expire. Dryden. 2. To give forth insensibly or gently, as a fluid or vapor; to emit in minut...