scrawny
Unhealthily thin and weak-looking, like not fed enough.
Scrawny means unhealthily thin and weak-looking, with visible bones and not much muscle. A scrawny person or animal looks undernourished, like they haven't been eating enough or growing properly. You might see a scrawny stray cat with its ribs showing, or notice that a plant looks scrawny when it hasn't gotten enough water or sunlight.
The word carries a negative feeling. It's different from simply being thin or slender, which can be perfectly healthy. Scrawny suggests something's wrong: not enough food, not enough strength, not enough care. A scrawny chicken in a farmer's coop might be sick or getting bullied away from the food by larger birds.
People sometimes use scrawny to describe someone who looks weak or underdeveloped, like a scrawny kid who gets picked last for basketball because he looks like he can't compete physically. But appearances can fool you. Many scrawny-looking people turn out to be surprisingly strong, quick, or capable. A scrawny dog who looked pitiful at the shelter might become energetic and healthy with proper care and feeding.