WordNet sense 1 (a state of decay usually accompanied by an offensive odor):

putrefaction

WordNet sense 2 ((biology) the process of decay caused by bacterial or fungal action):

decomposition, rotting

WordNet sense 3 (unacceptable behavior (especially ludicrously false statements)):

buncombe, bunk, bunkum, guff, hogwash

WordNet sense 4 (break down):

decompose, molder, moulder

WordNet sense 5 (waste away):

waste