As"tro*labe (ăs"tr&osl;*lāb), n. [OE. astrolabie, astrilabe, OF. astrelabe, F. astrolabe, LL. astrolabium, fr. Gr. 'astrola`bon; 'a`stron star + &?;, &?;, to take.] 1. (Astron.) An instrument for observing or showing the positions of the stars. It is now disused.

&fist; Among the ancients, it was essentially the armillary sphere. A graduated circle with sights, for taking altitudes at sea, was called an astrolabe in the 18th century. It is now superseded by the quadrant and sextant.

2. A stereographic projection of the sphere on the plane of a great circle, as the equator, or a meridian; a planisphere. Whewell.

• An astronomical and navigational instrument for gauging the altitude of the Sun and stars.