Armil \Ar"mil\, n. [L. armilla a bracelet, fr. armus arm: cf. OF. armille.] 1. A bracelet. [Obs.] 2. An ancient astronomical instrument. Note: When composed of one ring placed in the plane of the equator for determining the time of the equinoxes, it is called an equinoctial armil; when of two or more rings, one in the plane of the meridian, for observing the solstices, it is called a solstitial armil. --Whewell.