[syn: once, formerly, at one time, erstwhile, erst]
The Collaborative International Dictionary of English v.0.48:
Erstwhile \Erst`while"\ (-hw[imac]l"), adv.
   Till then or now; heretofore; formerly. [Archaic] Erubescence
WordNet (r) 3.0 (2006):
erstwhile
    adv 1: at a previous time; "at one time he loved her"; "her
           erstwhile writing"; "she was a dancer once"; [syn:
           once, formerly, at one time, erstwhile, erst]
    adj 1: belonging to some prior time; "erstwhile friend"; "our
           former glory"; "the once capital of the state"; "her
           quondam lover" [syn: erstwhile(a), former(a), old,
           onetime(a), one-time(a), quondam(a), sometime(a)]
Moby Thesaurus II by Grady Ward, 1.0:
27 Moby Thesaurus words for "erstwhile":
   already, ancient, bygone, earlier, early, fore, former, formerly,
   heretofore, immemorial, late, old, olden, once, onetime, past,
   prehistoric, previous, previously, primeval, primitive, prior,
   quondam, recent, sometime, then, whilom