Can I Get The Meaning Of This Word Elswhilst? Any English Word Like That?

The word you want could be ELSEWHERE, meaning somewhere else ("I was elsewhere when the crime took place, so I didn't see anything."

But if you're looking for an unusual word, it's probably ERSTWHILE. This is an adjective meaning "former" or "previous." It's very formal and now rarely used at all. An example sentence might be "Bill Clinton is the erstwhile President of the United States." It comes from the old German word erst, or "first."