letup vs intermission

letup and intermission both are nouns.

Word	Noun	Adjective	Verb	Adverb
letup	Yes	No	No	No
intermission	Yes	No	No	No

As nouns, intermission is a hypernym of letup; that is, intermission is a word with a broader meaning than letup:

letup: a pause during which things are calm or activities are diminished
intermission: a time interval during which there is a temporary cessation of something

Other hypernyms of letup include break, interruption, pause, suspension.

letup (noun)	intermission (noun)
a pause during which things are calm or activities are diminished	the act of suspending activity temporarily
	a time interval during which there is a temporary cessation of something