Definition of "caftan"

From the pocket of her discarded caftan she lifted a thick medallion and set it in place around her neck.

1989, Dan Simmons, Hyperion, London: Headline, published 1991, page 456

Still, he did look striking in his long white flowing pants and a white caftan.

2018, Nnedi Okorafor, Who Fears Death, HarperVoyager, page 12