particle
Sentence-ending particle used in casual male speech to mark a wh-question (what, where, who, etc.) with a familiar, often rhetorical or emphatic tone. Similar to だい but with a slightly rougher or more masculine feel.
See also: だい
何がおかしいんじゃい。
What's so funny?
誰がそんなこと言ったんじゃい。
Who said such a thing?