Definitions

from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun One eighth of a circle.
  • noun A 45° arc.
  • noun The area enclosed by two radii at a 45° angle and the intersected arc.
  • noun An instrument based on the principle of the sextant but employing only a 45° angle, used as an aid in navigation.
  • noun Astronomy The position of a celestial body when it is separated from another by a 45° angle.
  • noun One of eight parts into which three-dimensional space is divided by three usually perpendicular coordinate planes.

from The Century Dictionary.

  • noun Each of the eight regions into which space is divided by three copunctal non-costraight planes.
  • noun The eighth part of a circle.
  • noun In astronomy, that position or aspect of two heavenly bodies, especially a planet and the sun, when half-way between conjunction or opposition and quadrature, or distant from one another by the eighth part of a circle, or 45°.
  • noun An instrument used by seamen for measuring angles, resembling a sextant or quadrant in principle, but having an arc the eighth part of a circle, or 45°. By double reflection it can measure an arc of 90°. See sextant. Hadley's quadrant is really an octant.

from the GNU version of the Collaborative International Dictionary of English.

  • noun (Geom.) The eighth part of a circle; an arc of 45 degrees.
  • noun (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.
  • 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.
  • noun (Math. & Crystallog.) One of the eight parts into which a space is divided by three coördinate planes.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun The eighth part of a circle; an arc of 45 degrees.
  • noun geometry : The eighth part of a disc; a sector of 45 degrees; half a quadrant.
  • noun nautical : An instrument for measuring angles, particularly of elevation.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun a measuring instrument for measuring angles to a celestial body; similar to a sextant but with 45 degree calibration

Etymologies

from The American Heritage® Dictionary of the English Language, 4th Edition

[Latin octāns, octant-, from octō, eight; see oktō(u) in Indo-European roots.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

From Latin octans

Examples

  • John Paul’s deliverance from the hardship of the lower deck was a brass instrument called an octant.

    John Paul Jones

  • John Paul’s deliverance from the hardship of the lower deck was a brass instrument called an octant.

    John Paul Jones

  • Advances in the development of these instruments made such calculations easier and more precise, for example: the "course protractor", the "cuadrant", the "octant and the sextant", and the "longitude clock", which was a precision chronometer.

    Sailing on and on

  • Advances in the development of these instruments made such calculations easier and more precise, for example: the "course protractor", the "cuadrant", the "octant and the sextant", and the "longitude clock", which was a precision chronometer.

    Sailing on and on

  • From a private collection, offerings include several important pairs of globes by Newton, a sextant by Ramsden, an octant by George Jones, equinoctial dials, astrolabes, chronometers, microscopes and nautical antiques.

    Useful and Beautiful Devices | clusterflock

  • Curved an eighth of circle, hence “octant”, fixed with small mirrors and etched by degrees, an octant can tell a mariner the angle of the sun to the horizon at high noon.

    John Paul Jones

  • It was in its octant, and showed a crescent finely traced on the dark background of the sky.

    Round the Moon

  • Curved an eighth of circle, hence “octant”, fixed with small mirrors and etched by degrees, an octant can tell a mariner the angle of the sun to the horizon at high noon.

    John Paul Jones

  • Wesley found a packet of small iron tools, an octant and a massive spiked club.

    DEBTOR'S PLANET

  • Charred remains of the boat, a burned octant, and a few unexploded cartridges were all that remained of the meager outfit upon which they depended to take them to the mouth of the river, a distance of over 250 miles.

    Scientific American Supplement No. 822, October 3, 1891

Comments

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  • "Octant or octile, in astronomy, the aspect of two planets, wherein they are distant an eight part of a circle, or 45 degrees from each other."

    Falconer's New Universal Dictionary of the Marine (1816), 326

    October 14, 2008