in the past : formerly
Under a search in Google News, the word ERSTWHILE is used mot frequently to describe a formerly filled position—the ERSTWHILE royal family, the ERSTWHILE editor, the ERSTWHILE administration. The word itself has a distinguished feel to it, giving the text in which it is used an air of sophistication.
Example, featured at movieline.com, October 12, 2010:
Fran Drescher: the flashy girl from Flushing, the authoress, and now, the host of your new favorite daytime talk show? The erstwhile star signed a three-week contract with Fox to front her own chatfest, beginning on Nov. 26. But is Fran Fine a palatable successor to Oprah?
Let's ignore the obvious and stay focused. In this context ERSTWHILE sticks out like fondue at an IHOP. The writer could have very well used "former," but instead went with the more cultivated choice. ERSTWHILE. The sound of the word feels similar to the sound of my roommate when she pronounces the word documentary as DOC-u-men-tary (as opposed to the more customary doc-u-MEN-tary). It's distracting, out-of-order, one of these things is not like the other. Yet she sounds distinguished when the act of extraordinary emphasis slips from her mouth.
Perhaps that's why a word like ERSTWHILE remains—to add a spice of refinement to ordinary American English. Or to add a bit of savoir vivre to Fran Drescher, who, in my opinion, worked well with the card she was dealt.