[ ahrk-too r-uh s, -tyoo r- ]
/ ɑrkˈtʊər əs, -ˈtyʊər- /

noun Astronomy.

a first-magnitude star in the constellation Boötes.

Origin of Arcturus

1352–75; < Latin < Greek Arktoûros, equivalent to árkt(os) bear + -oûros keeper; replacing Middle English arture < Middle French

Related forms

Arc·tu·ri·an, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for arcturus

British Dictionary definitions for arcturus


/ (ɑːkˈtjʊərəs) /


the brightest star in the constellation Boötes: a red giant. Visual magnitude: –0.4; spectral type: K2III; distance: 37 light years

Derived Forms

Arcturian, adjective

Word Origin for Arcturus

C14: from Latin, from Greek Arktouros, from arktos bear + ouros guard, keeper
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

Science definitions for arcturus


[ ärk-turəs ]

A giant star in the constellation Boötes. It is the brightest star in the Northern Hemisphere and the fourth brightest star in the sky, with an apparent magnitude of 0.00. Scientific name: Alpha Boötes.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.