Phthisic is a rare medical term that refers to a condition marked by emaciation, weakness, and wasting away of the body. Synonyms for this obscure term include tubercular, consumptive, cachectic, and marasmic. These words all describe a person who is suffering from a severe and prolonged illness that causes extreme weight loss, fatigue, and general decline in health. Other words that can be used to convey a similar meaning to phthisic include anemic, haggard, gaunt, and frail. While the condition may be rare, having a range of synonyms to describe it can be enormously helpful when it comes to effective communication in the medical field.