Noah Webster's New International Dictionary of the English Language

1. (superl.) Slow of understanding; wanting readiness of apprehension; stupid; doltish; blockish.

2. (superl.) Slow in action; sluggish; unready; awkward.

3. (superl.) Insensible; unfeeling.

4. (superl.) Not keen in edge or point; lacking sharpness; blunt.

5. (superl.) Not bright or clear to the eye; wanting in liveliness of color or luster; not vivid; obscure; dim; as, a dull fire or lamp; a dull red or yellow; a dull mirror.

6. (superl.) Heavy; gross; cloggy; insensible; spiritless; lifeless; inert.

7. (superl.) Furnishing little delight, spirit, or variety; uninteresting; tedious; cheerless; gloomy; melancholy; depressing; as, a dull story or sermon; a dull occupation or period; hence, cloudy; overcast; as, a dull day.

8. (v. t.) To deprive of sharpness of edge or point.

9. (v. t.) To make dull, stupid, or sluggish; to stupefy, as the senses, the feelings, the perceptions, and the like.

10. (v. t.) To render dim or obscure; to sully; to tarnish.

11. (v. t.) To deprive of liveliness or activity; to render heavy; to make inert; to depress; to weary; to sadden.

12. (v. i.) To become dull or stupid.