Merriam-Webster Collegiate Dictionary - dull

 I. adjective  Etymology: Middle English dul; akin to Old English dol foolish, Old Irish dall blind  Date: 13th century  1. mentally slow ; stupid  2.  a. slow in perception or sensibility ; insensible somewhat ~ of hearing  b. lacking zest or vivacity ; listless a ~ performance  3. slow in action ; sluggish  4.  a. lacking in force, intensity, or sharpness a ~ ache  b. not resonant or ringing a ~ booming sound  5. lacking sharpness of edge or point a ~ knife  6. lacking brilliance or luster a ~ finish  7. of a color low in saturation and low in lightness  8. cloudy ~ weather  9. tedious, uninteresting ~ lectures  • ~ness also dulness noun  • ~y adverb Synonyms:  ~, blunt, obtuse mean not sharp, keen, or acute. ~ suggests a lack or loss of keenness, zest, or pungency a ~ pain a ~ mind. blunt suggests an inherent lack of sharpness or quickness of feeling or perception a person of blunt sensibility. obtuse implies such bluntness as makes one insensitive in perception or imagination too obtuse to take the hint.  Synonym: see in addition stupid.  II. verb  Date: 13th century  transitive verb to make ~ ~ a knife's edge  intransitive verb to become ~