There are several synonyms for the phrase "waste away," including wither, decline, degenerate, deteriorate, and languish. Withering typically refers to losing strength or vitality, often due to lack of nourishment or exposure to harsh conditions. Decline and degenerate suggest a gradual deterioration of physical or mental capability. Deteriorate usually refers to a decline or disintegration of something physical. Languish describes a state of being weak or apathetic, often due to prolonged suffering or imprisonment. These terms can be used interchangeably with "waste away" to describe a variety of situations, from physical health to mental state.