a unit of length, equal to the mean distance of the earth from the sun: approximately 93 million miles (150 million km). Abbreviation: AU
Five English Words That Are Utterly UniqueAmazingly, the only English word with three Ys also happens to describe a rare astronomical event involving three heavenly bodies.
Origin of astronomical unit
First recorded in 1900–05
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for astronomical unit
a unit of distance used in astronomy equal to the mean distance between the earth and the sun. 1 astronomical unit is equivalent to 1.495 × 10 11 metres or about 9.3 × 10 7 miles
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 astronomical unit
[ ăs′trə-nŏm′ĭ-kəl ]
A unit of length equal to the average distance from Earth to the Sun, approximately 149.6 million km (92.8 million mi). It is used especially to measure distances within the solar system. Compare light-year parsec.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Culture definitions for astronomical unit
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.