In a straight line, by the shortest route, as in It's only a mile as the crow flies, but about three miles by this mountain road. This idiom is based on the fact that crows, very intelligent birds, fly straight to the nearest food supply. [Late 1700s]

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Company. All rights reserved.