Or search: dim, mat, arid, damp, drab, dumb, matt, mute, numb, pall, blunt, dense, matte, muted, boring
2 Syllables: SU
bloodless, buckets, buffet, bulbous, buttocks, buttress, couplets, covet, Douglas, Duchess, dullness, dulness, justice, Justus, luckless, lustrous, musket, oneness, pumice, puppet, roughest, stirrup, stomach, Suffolk, summit, syrup, toughest, troublous, turret
3 Syllables: USU
Augustus, Republic, rivulets

Found 32 words across 2 groupings. Skipped 7 excess words of a similar stem.