overlapping so as to provide a double thickness of material across the chest, and having a double row of buttons: said as of a coat
See double-breasted in American Heritage Dictionary 4
(dŭbˈəl-brĕsˈtĭd)
adjective
Fastened by lapping one edge of the front of a garment well over the other and usually having a double row of buttons with a single row of buttonholes. Used especially of a coat or jacket.
Having a double-breasted coat: a double-breasted suit.