In its original sense, a shaggy dog story is an extremely long-winded anecdote characterized by extensive narration of typically irrelevant incidents and terminated by an anticlimax or a pointless punchline.

Shaggy dog stories play upon the audience's preconceptions of joke-telling. The audience listens to the story with certain expectations, which are either simply not met or met in some entirely unexpected manner. A lengthy shaggy dog story derives its humour from the fact that the joke-teller held the attention of the listeners for a long time (such jokes can take five minutes or more to tell) for no reason at all, as the end resolution is essentially meaningless.