housecoat

noun2

1. •
   (US, Canada) A bathrobe or dressing gown.
2. •
   (Australia) A longish dress-like garment of one piece, fastening down the front, worn about the house.

   • Her housecoat had fallen open. She was wearing only panties and bra, which did nothing to make her scrawny, wrinkled body appealing. — 1968