Become or make someone aware of the truth of a situation, as in It's time you opened your eyes to the politics of this office, or The trip to Zimbabwe opened her eyes to the difficulties faced by developing nations. [Second half of 1800s]

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.