Definitions

1. noun

A waterproof or water-resistant layer, typically nylon or polyester, attached to a sleeping bag or backpack to provide protection from the elements.

“She pitched the flysheet over the picnic area to shield us from the sun.”

2. noun

A detachable fabric cover, often used to provide weather protection for a vehicle or other outdoor equipment.

“The flysheet on his pickup truck helped keep the rain out while he was working on it.”