dull - verb

• make dull in appearance
• become dull or lusterless in appearance; lose shine or brightness
• deaden (a sound or noise), especially by wrapping
• make numb or insensitive
• make dull or blunt
• become less interesting or attractive
• make less lively or vigorous

dull - adjective

• lacking in liveliness or animation
• emitting or reflecting very little light
• not keenly felt
• not having a sharp edge or point
• being or made softer or less loud or clear
• so lacking in interest as to cause mental weariness
• (of color) very low in saturation; highly diluted
• slow to learn or understand; lacking intellectual acuity
• (of business) not active or brisk
• blunted in responsiveness or sensibility
• not clear and resonant; sounding as if striking with or against something relatively soft
• darkened with overcast

dull - thesaurus

benumb   blunt   boring   damp   dampen   deadening   dense   dim   dumb   irksome   leaden   muffle   muffled   mute   muted   numb   obtuse   pall   slow   sluggish   softened   tedious   thudding   tiresome   wearisome