left: 25px">·noun The eighth part of a circle; an arc of 45 degrees.
left: 25px">II. Octant ·noun One of the eight parts into which a space is divided by three coordinate planes.
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III. Octant ·noun An instrument for measuring angles (generally called a quadrant), having an arc which measures up to 9O°, but being itself the eighth part of a circle.
·cf. Sextant.
left: 25px">IV. Octant ·noun 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.