1. In a small quantity or extent
   "spread the margarine thinly over the meat";
   - lightly
    
2. In a widely distributed manner
   "thinly overgrown mountainside"
    
3. Without viscosity
   "the blood was flowing thinly";
   - thin
    
4. Without force or sincere effort
   "smiled thinly"

Antonym: thickly