From Longman Dictionary of Contemporary Englishhousecoathouse‧coat /ˈhaʊs-kəʊt $ -koʊt/ noun [countable] DCCa long loose coat worn at home to protect clothes while cleaning etc
Examples from the Corpus
housecoat• She felt hot and sticky and changed her clothes and put on a housecoat.• She was wearing a housecoat and slippers.• She rose late and was still in a négligé and housecoat.• She stood there in the doorway, wearing a loose blue housecoat.• She was wearing a quilted housecoat, and in her hand was a hairdryer.• She is a pretty, older woman dressed in a flowery silk housecoat.• Mrs Sweet stood up and stripped off the housecoat. 