misfire vs break down

misfire is a noun but break down is not a noun.

Word	Noun	Adjective	Verb	Adverb
misfire	Yes	No	Yes	No
break down	No	No	Yes	No

As verbs, break down is a hypernym of misfire; that is, break down is a word with a broader meaning than misfire:

Other hypernyms of misfire include break, conk out, die, fail, give out, give way, go, go bad.

misfire (noun)	break down (noun)
an explosion that fails to occur
a failure to hit (or meet or find etc)

misfire (verb)	break down (verb)
fail to fire or detonate	collapse due to fatigue, an illness, or a sudden attack
	stop operating or functioning
	separate (substances) into constituent elements or parts
	make a mathematical, chemical, or grammatical analysis of; break down into components or essential features
	make ineffective
	cause to fall or collapse
	lose control of one's emotions
	fall apart