Meta-joke refers to several somewhat different, but related categories: self-referential jokes, jokes about jokes (also known as metahumor), and joke templates.
This kind of meta-joke is a joke in which a familiar class of jokes is part of the joke. Examples of meta-jokes:
Meta-humor is humor about humor. Here meta is used to describe that the joke explicitly talks about other jokes, a usage similar to the words metadata (data about data), metatheatrics (a play within a play, as in Hamlet), and metafiction.
Marc Galanter in the introduction to his book Lowering the Bar: Lawyer Jokes and Legal Culture cites a meta-joke in a speech of Chief Justice William Rehnquist:
I've often started off with a lawyer joke, a complete caricature of a lawyer who's been nasty, greedy, and unethical. But I've stopped that practice. I gradually realized that the lawyers in the audience didn't think the jokes were funny and the non-lawyers didn't know they were jokes.
E. B. White has joked about humor, saying that "Humor can be dissected, as a frog can, but the thing dies in the process and the innards are discouraging to any but the pure scientific mind."
Another kind of meta-humor is when jokes make fun of poor jokes by replacing a familiar punchline with a serious or nonsensical alternative. Such jokes expose the fundamental criterion for joke definition, "funniness", via its deletion. Comedians such as George Carlin and Mitch Hedberg used metahumor of this sort extensively in their routines. Hedberg would often follow up a joke with an admission that it was poorly told, or insist to the audience that "that joke was funnier than you acted." These follow-ups usually get laughs superior to those of the perceived poor joke and serve to cover an awkward silence. Johnny Carson, especially late in his Tonight Show career, used to get uproarious laughs when reacting to a failed joke with, for example, a pained expression. Immediately following a failed joke about Lincoln's death, for instance, Carson remarked, "A hundred years later, and you still can't do Abraham Lincoln jokes." The latter remark got a better laugh. Similarly, Jon Stewart, when hosting his own television program, used to wring his tie and grimace following an uncomfortable clip or jab. Eddie Izzard often reacts to a failed joke by miming writing on a paper pad and murmuring into the microphone something along the lines of "must make joke funnier" or "don't use again" while glancing at the audience.