Source : Webster's Revised Unabridged Dictionary (1913)

Expiratory \Ex*pir"a*to*ry\, a. (Physiol.)
   Pertaining to, or employed in, the expiration or emission of
   air from the lungs; as, the expiratory muscles.

Source : WordNet®

expiratory
     adj : of or relating to the breathing out phase of respiration