Experienced or achieved, as in Once a medical student has anatomy under her belt, she'll have much less to memorize. This metaphoric expression likens food that has been consumed to an experience that has been digested. [Colloquial; first 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.