PUTREFY

to rot

to decay and give off a foul odor

/become putrid

"he had wondered what was causing the horrible stench in his apartment and then he saw the rat which had putrefied next to his bed."

"He knew that after the old man died he would putrefy so keeping him in the house was not an option."

"she pondered for a moment on why when alive the human body doesn't smell, but then when it dies it putrefies."