The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
PRONUNCIATION: ûrst'hwīl', -wīl'
ADVERB: In the past; at a former time; formerly.
ADJECTIVE: Former: our erstwhile companions.
The American Heritage® Dictionary of the English Language, Fourth Edition. Copyright © 2000 by Houghton Mifflin Company. Published by the Houghton Mifflin Company. All rights reserved.
Bringing to mind our erstwhile Board God from a former forum, Brad Ross-McLeod.