thigh-slapper vs gag

thigh-slapper and gag both are nouns.

Word	Noun	Adjective	Verb	Adverb
thigh-slapper	Yes	No	No	No
gag	Yes	No	Yes	No

As nouns, gag is a hypernym of thigh-slapper; that is, gag is a word with a broader meaning than thigh-slapper:

Other hypernyms of thigh-slapper include jape, jest, joke, laugh.

thigh-slapper (noun)	gag (noun)
a joke that seems extremely funny	restraint put into a person's mouth to prevent speaking or shouting
	a humorous anecdote or remark intended to provoke laughter

thigh-slapper (verb)	gag (verb)
	struggle for breath; have insufficient oxygen intake
	make an unsuccessful effort to vomit; strain to vomit
	cause to retch or choke
	make jokes or quips
	be too tight; rub or press
	tie a gag around someone's mouth in order to silence them
	prevent from speaking out