something said or done to provoke laughter or cause amusement, as a witticism, a short and amusing anecdote, or a prankish act: He tells very funny jokes. She played a joke on him.
something that is amusing or ridiculous, especially because of being ludicrously inadequate or a sham; a thing, situation, or person laughed at rather than taken seriously; farce: Their pretense of generosity is a joke. An officer with no ability to command is a joke.
a matter that need not be taken very seriously; trifling matter: The loss was no joke.
something that does not present the expected challenge; something very easy: The test was a joke for the whole class.