[sek-stuh nt]


an astronomical instrument used to determine latitude and longitude at sea by measuring angular distances, especially the altitudes of sun, moon, and stars.
(initial capital letter) Astronomy. the constellation Sextans.

Origin of sextant

1590–1600; < Latin sextant- (stem of sextāns) sixth part of a unit. See sext1, -ant
Can be confusedsextant sextet sexton Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for sextant

Historical Examples of sextant

  • Dontor glanced at the juniors, saw that Kuero had his sextant ready, and raised his own.

    The Players

    Everett B. Cole

  • Prof. had forgotten his sextant and rode back to our main camp for it.

    A Canyon Voyage

    Frederick S. Dellenbaugh

  • Forsythe made a notation from the sextant on a piece of paper.

    The Wreck of the Titan

    Morgan Robertson

  • The sextant is the one most in use and so will be described first.

    Lectures in Navigation

    Ernest Gallaudet Draper

  • Now read the angle of the height of that light by using your sextant.

    Lectures in Navigation

    Ernest Gallaudet Draper

British Dictionary definitions for sextant



an optical instrument used in navigation and consisting of a telescope through which a sighting of a heavenly body is taken, with protractors for determining its angular distance above the horizon or from another heavenly body
a sixth part of a circle having an arc which subtends an angle of 60°

Word Origin for sextant

C17: from Latin sextāns one sixth of a unit
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for sextant

instrument for determining latitude, 1620s, from Modern Latin sextans, said to have been coined c.1600 by Danish astronomer Tycho Brahe, from Latin sextans "a sixth," from sex "six" (see six). So called because the sextans has a graduated arc equal to a sixth part of a circle.

Online Etymology Dictionary, © 2010 Douglas Harper

sextant in Science



An instrument containing a graduated 60° arc and a movable pivoted arm corresponding to the radius of the arc's circle, used in celestial navigation to measure the altitude of a celestial body in order to determine the observer's latitude and longitude. A horizontally mounted telescope and two small mirrors are arranged so that the observer can, by moving the pivoted arm, sight the horizon and the reflected image of the celestial body in the same line, giving a reading along the arc that is used to look up the observer's position in a published table.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.