Definition of "astronomical unit" []

• A unit of length used in measuring astronomical distances within the solar system equal to the mean distance from Earth to the sun, approximately 150 million kilometers (93 million miles). (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "At thirty hours per light-year, the Mitsuushi StarDrive chewed up an astronomical unit every 1.7 seconds, and even with computer control a ship was lucky to make breakout within a half-million kilometers of its projected target."