1. To affect someone or something with or cause someone or something to undergo decay or decomposition. The disease causes necrosis, gradually rotting away at the patient's flesh. The moisture has been rotting away at the walls of the house.

2. To afflict someone with some persistent, agonizing feeling or emotion. The guilt has been rotting away at me ever since I stole that money. It's the kind of guilt that can rot away at you for years.

3. To waste one's life at some location. I don't want to rot away at some retirement home when I'm older. Ever since he lost his job he's just been smoking weed and rotting away at home.