dull / dəl/ • adj. 1. lacking interest or excitement: your diet doesn't have to be dull and boring. ∎ archaic (of a person) feeling bored and dispirited: she said she wouldn't be dull and lonely.2. lacking brightness, vividness, or sheen: his face glowed in the dull lamplight| his black hair looked dull. ∎ (of the weather) overcast; gloomy: next morning dawned dull. ∎ (of sound) not clear; muffled: a dull thud of hooves. ∎ (of pain) indistinctly felt; not acute: there was a dull pain in his lower jaw. ∎ (of an edge or blade) blunt: a lot more people are cut with dull knives than with sharp ones.3. (of a person) slow to understand; stupid: the voice of a teacher talking to a rather dull child. ∎ archaic (of a person's senses) not perceiving things distinctly; insensitive. ∎ (of activity) sluggish, slow-moving: gold closed lower in dull trading.• v. make or become dull or less intense: [tr.] time dulls the memory | [intr.] Albert's eyes dulled a little. PHRASES: (as) dull as dishwater extremely dull.dull the edge of cause to be less keenly felt; reduce the intensity or effectiveness of: she'd have to find something to dull the edges of the pain.DERIVATIVES: dull·ish adj.dull·ness (also dul·ness) n.dul·ly adv.