a triviality not to be taken seriously(noun.attribute)
Example: I regarded his campaign for mayor as a joke.
source: wordnet30
Something said for the sake of exciting a laugh; something witty or sportive (commonly indicating more of hilarity or humor than jest); a jest; a witticism; as, to crack good-natured jokes.(noun)
source: webster1913
verb (v)
tell a joke; speak humorously(verb.communication)
Example: He often jokes even when he appears serious.