oc·​tant | \ ˈäk-tənt How to pronounce octant (audio) \

Definition of octant

1 : an instrument for observing altitudes of a celestial body from a moving ship or aircraft
2 : any of the eight parts into which a space is divided by three coordinate planes

Examples of octant in a Sentence

Recent Examples on the Web There is no way for such a locus to exist only in opposing octants of a cube. Quanta Magazine, "Solution: ‘The Slippery Math of Causation’," 29 June 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'octant.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of octant

1672, in the meaning defined at sense 1

History and Etymology for octant

Latin octant-, octans eighth of a circle, from octo

Keep scrolling for more

Learn More about octant

Time Traveler for octant

Time Traveler

The first known use of octant was in 1672

See more words from the same year

Statistics for octant

Cite this Entry

“Octant.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/octant. Accessed 19 Jan. 2021.

More from Merriam-Webster on octant

Britannica.com: Encyclopedia article about octant

Comments on octant

What made you want to look up octant? Please tell us where you read or heard it (including the quote, if possible).


Test Your Vocabulary

Words of Snow and Ice Quiz

  • image1037863653
  • Which of the following refers to thin, bending ice, or to the act of running over such ice?
True or False

Test your knowledge - and maybe learn something along the way.


Anagram puzzles meet word search.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!