Lacking brightness, interest, or sharpness. 'Dull' can describe a lack of intensity in color, a lack of excitement or stimulation, or a lack of keenness in intellect or a physical edge.
It suggests a state of being uninspiring, tedious, or blunt. The degree of 'dullness' can range from mildly uninteresting to severely lacking in impact or effectiveness.
DRY DIM DDY MAT
SLOW DRAB BLAH FLAT MATT TAME GREY PALL NUMB DUMB DAMP MUTE
HOHUM BLAND MATTE NOFUN VAPID BLUNT DINGY DREAR DENSE HOHUM MUTED DOWDY LEADY PROSY
BORING JEJUNE OBTUSE OPAQUE CLOUDY STUPID STODGY BENUMB DAMPEN MUFFLE LEADEN DREARY STOLID SOMBRE GLOOMY
MUNDANE TEDIOUS PROSAIC HUMDRUM INSIPID IRKSOME MUFFLED
TIRESOME SLUGGISH SOFTENED THUDDING TONEDOWN UNLIVELY OVERCAST
SLOWITTED DEADENING WEARISOME CHEERLESS
LACKLUSTER LACKLUSTRE UNEXCITING UNORIGINAL LACKLUSTER MONOTONOUS
DESENSITIZE UNINSPIRING
UNINTERESTING UNINTELLIGENT UNIMAGINATIVE