dressing gown

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A robe worn for lounging or before dressing.

from The Century Dictionary.

• noun A loose and easy gown or robe worn while making the toilet or when in dishabille.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An item of clothing often made from cotton or another absorbent material, in the form of a long open robe with a belt to tie it around the middle and fasten it securely; often worn over pyjamas.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a robe worn before dressing or while lounging