The phrase "skin and bone" is commonly used to describe someone who is extremely thin or emaciated. However, there are many other synonyms for this phrase that can be used to convey the same meaning such as skinny, boney, gaunt, lean, thin, scrawny, and undernourished. Each of these words can be used to describe someone who is lacking in body mass or muscle, and therefore appear frail and weak. When writing about someone who is "skin and bone," it is important to choose words that aptly describe their physical appearance without being disrespectful or insensitive.