\As"tro*labe\ ([a^]s"tr[-o]*l[=a]b), 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.
Note: 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 It is now superseded by the quadrant and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.