To attempt a comedic delivery and fail miserably for one of two reasons.
1. Immediately repeating a joke said by someone else in slightly different words.
2. Beginning an anecdote with painful pauses and trailing off into an embarrassed mumble, forgetting the punch line and leaving all onlookers angry, frustrated and tired.
Dave: "Yeah, that reminds me of the time that a guy I knew saw a guy playing the spoons, and then... erm... aww.. how do you say it again?.. Ok, I'll stop speaking now."