Webster's Revised Unabridged Dictionary · 1913

Nostril

Nostril , noun

[Old English nosethril, nosethirl, Anglo-Saxon nosþyrl; nos for nosu nose + þyrel opening, hole, from þyrel pierced, for þyrhel, from purh through. r261. See Nose, and Through, and compare Thrill.]

1.
(Anatomy) One of the external openings of the nose, which give passage to the air breathed and to secretions from the nose and eyes; one of the anterior nares.

In sperm whales, porpoises, and allied animals, there is only one nostril, which is situated on the top of the head and called a spiracle.

2.
Perception; insight; acuteness. [Obsolete]
Methinks a man Of your sagacity and clear nostril should Have made another choice. — B. Jonson