from The American Heritage® Dictionary of the English Language, 4th Edition
- adv. In the past; at a former time; formerly.
- adj. Former: our erstwhile companions.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adv. Formerly; in the past.
- adj. Former, previous.
from the GNU version of the Collaborative International Dictionary of English
- adv. Till then or now; heretofore; formerly.
from The Century Dictionary and Cyclopedia
- At one time; formerly.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. belonging to some prior time
- adv. at a previous time
erst + while (Wiktionary)