thin is an English adjective meaning having little, or too little, flesh or fat on the body.
Other meanings of thin include:
1. (of a garment or other material) made of light material
2. (of a liquid substance) not containing much solid; flowing easily
3. having few parts or members relative to the area covered or filled; sparse
4. (of a sound) lacking resonance or volume
5. (of an excuse or explanation) weak and unconvincing