Synonyms for Break down:

n.

falter, misfire, go down, malfunction, flop, fizzle, backfire, miss, languish, cease, succumb, roll up. go off, shut off, burn out. batter, thump, bang, punch, HIT, knock. choke up, cry, weep, dissolve into, burst out, cry/sob your heart out, howl, wail. break down (noun)
analyze, fail, crumble, conk out, crush, take apart, dissect, tumble, die, go bad, analyse, break, crumple, lose it, go, decompose, collapse, give way, give out.

v.

act up (malfunction) (verb)
conk out.
choke up (verb)
cry.
competition (verb)
crush.
crack (verb)
give way, collapse, lose it, succumb.
crumple (verb)
crush.
cry (verb)
howl, choke up, wail, weep.
decompose (verb)
crumble, dissect, atomize.
die (verb)
fail, go bad.
dissect (verb)
investigate.
divide (verb)
branch.
fail (verb)
flop, fizzle, go down, miss.
fall (verb)
tumble.
founder (verb)
misfire.
misfire (verb)
backfire.
perish (verb)
cease, go.
rot (verb)
languish.
spoil (verb)
go off.
succumb (verb)
give out.

Other synonyms:

boil. go off. branch. go down. analyze
dissect.
cry
weep.
die
go bad.
disintegrate
take apart.
dissect
dissect.
fail
misfire.