See erstwhile in Webster's New World Roget's A-Z Thesaurus II
adverb
At a time in the past:
already, before, earlier, formerly, once, previously. (Archaic) aforetime, beforetime. See precede
adjective
Having been such previously:
former, late, old, once, onetime, past, previous, quondam, sometime, whilom. See precede
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