A shirt worn over another shirt or over other clothing without being tucked into the waistband.(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.
Use "overshirt" in a sentence
"He began to unbutton her overshirt, letting the air hold her leash in place through one of his little magic tricks, and the smile on her face vanished, replaced by a thin rigid line of null expression."
"On my way out I grabbed my jacket, an insulated flannel overshirt."
"He was dressed casually, in loose slacks and an even looser shirt and overshirt, and his high forehead creased a little as the newsreader continued her report."