Dullest

adjective

1. Lacking the ability to cut easily; not sharp.

   "All these knives are dull."

2. Boring; not exciting or interesting.

   "He sat through the dull lecture and barely stayed awake."

3. Not shiny; having a matte finish or no particular luster or brightness.

   "Choose a dull finish to hide fingerprints."

4. Not bright or intelligent; stupid; having slow understanding.
5. Sluggish, listless.