Wiktionary
oversheet
n. A sheet placed over the top of something.
Usage examples of "oversheet".
He was drawing up the gold-embroidered oversheet when he heard the door through which he had entered the boudoir open.
As she spoke, she pushed aside the oversheet and the red silk sheet, revealing remarkably rounded breasts and a small waist.
The pillow yielded beneath him, soft and inviting, and he felt the blankets and a soft oversheet being drawn up around his thin shoulders.