in-joke vs jape

in-joke and jape both are nouns.

Word	Noun	Adjective	Verb	Adverb
in-joke	Yes	No	No	No
jape	Yes	No	No	No

As nouns, jape is a hypernym of in-joke; that is, jape is a word with a broader meaning than in-joke:

in-joke: a joke that is appreciated only by members of some particular group of people
jape: a humorous anecdote or remark intended to provoke laughter

Other hypernyms of in-joke include gag, jest, joke, laugh.

in-joke (noun)	jape (noun)
a joke that is appreciated only by members of some particular group of people	a humorous anecdote or remark intended to provoke laughter