see under of age.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
Examples from the Web for under-age
We heard multiple reports of proxy and under-age voting and ballot stuffing, and bias by Independent Election Commission staff.Was the Women's Vote Counted?
September 12, 2009
Those are the very hours you under-age fellows are not here.The Story of Leather
Sara Ware Bassett
Two under-age girls were found there, but the madam got off with a fine and the girls disappeared.