As″tro‐labe (ăs″trō̍‐lāb), n. [OE. astrolabie, astrilabe, OF. astrelabe, F. astrolabe, LL. astrolabium, fr. Gr. αστρολἄβον; ἄστρον star + �, �, to take.] 1. (Astron.) An instrument for observing or showing the positions of the stars. It is now disused.
☞ 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 It is now superseded by the quadrant and sextant.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.