The act of getting some cheap laughs by pooping one's pants.
Billy's lame jokes kept falling flat, so, desperate for a laugh, he decided to change course and try some self-defecating humor.
Not to be confused with self-deprecating humor, self-defecating humor is NOT funny. A joke that bombs like a dump of crap.
Example: A joke about your own foibles that stinks!
Sorry,Man, I hate to admit it, but I like PB&J with bacon even though it always gives me gas. (Your admitting that is self-defecating humor.)
Too much information, Dude!