[1] : The Collaborative International Dictionary of English v.0.48

octant \oc"tant\, n. l. octans, -antis. fr. octo eight. see
   octave.
   1. geom. the eighth part of a circle; an arc of 45 degrees.
      1913 webster

   2. astron.  astrol. the position or aspect of a heavenly
      body, as the moon or a planet, when half way between
      conjunction, or opposition, and quadrature, or distant
      from another body 45 degrees.
      1913 webster

   3. an instrument for measuring angles generally called a
      quadrant, having an arc which measures up to 9odeg,
      but being itself the eighth part of a circle. cf.
      sextant.
      1913 webster

   4. math.  crystallog. one of the eight parts into which a
      space is divided by three coordinate planes.
      1913 webster
see also:
octave quadrant sextant 

[2] : WordNet (r) 2.0

octant
     n : a measuring instrument for measuring angles to a celestial
         body; similar to a sextant but with 45 degree calibration

Octant >> O Words
Octant, definition of term: Octant
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