What does the phrase "catch 22" mean?

The term "catch 22" is a frustrating situation in which one is trapped by contradictory regulations or paradoxical rules. The term originated from Joseph Heller's 1961 novel of the same name, "Catch 22."

In Heller's novel, the catch is that a bomber pilot will be considered insane by his superiors if he flies combat missions without asking to be relieved from duty, and would therefore be eligible to be relieved from duty. But, if he asks to be relieved from duty, then his superiors will consider him sane and he will have to keep flying. In 1970, a movie was released based on the book, which led to widespread use of the term.