1. In accordance with what is appropriate or suitable for the circumstances
   "I met the junior senator from Illinois and I was duly impressed";
   - appropriately, suitably, fittingly, befittingly, fitly, properly, appositely, correctly
    
2. As expected or required
   "The ceremony was duly performed at noon"
    
3. At the proper time; punctually
   "The train arrived duly at 9 o'clock"

Antonym: unsuitably

Encyclopedia: Duly