Underwear, particularly men's underwear. "BVD" is an underwear manufacturer. Shut the door, I don't want anyone to see me in my BVDs!
BVDs
and beeveedees
n. underwear; men’s underwear. (The first entry is an initialism. From Bradley, Voorhies, and Day, the manufacturers. Always plural.) He stood there in his BVDs, freezing.