The term "Jeopardy Reject" is not only a literal term, but also used as an insult, primarily in intellectual circles, generally as a chiding comment on the ability of a friend or colleague to produce knowledge outside of his or her field. For example, a person who can quote the entirety of the proof that "the rational numbers are a countable set", yet cannot name 25 U.S. states if asked, may be referred to as a "Jeopardy Reject" by their friends. (Not that this ever happened to anyone or anything...;)
On a different note, many people who are actually selected as contestants on the game show nonetheless prove poor participants, as the pressure of the situation saps their otherwise competent intellect.