Nōs'tril, n.

n. [O. Eng. nosethril, nosthiril, A-S. nasthyril, nāsthyril, from nosu, nose, and thyrl, thyrel, hole, aperture; thyrlian, thyrelian, to make a hole, to bore, drill; O. Fries. nosterle.]

1. One of the two elliptical apertures situated below the extremity of the nose, and separated by a cartilaginous membrane, which give passage to the air we breathe, and to the secretions of the nose. [Formerly written also nosthril and nosthrill.]
2. Hence, perception; insight. [Obs.]

Methinks a man Of your sagacity and clear nostril should Have made a better choice. B. Jonson.