| monotonous(adjective, dull, quiet, weak, simple) |
| mooney(adjective, dull, slow, heavy, sluggish) |
| moony(adjective, dull, heavy, indifferent, stupid) |
| mopey(adjective, dull, unhappy, dark, gloomy) |
| mopy(adjective, dull, flat, low, sad) |
| mothballed(adjective, dull, idle, sluggish, lazy) |
| motionless(adjective, dull, idle, sluggish, lazy) |
| mournful(adjective, dull, unhappy, dark, gloomy) |
| muted(adjective, dull, weak, flat, dead) |
| narcotic(adjective, quiet, slow, heavy, sleepy) |
| nebbish(adjective, dull, stupid, idle, weary) |
| nothing(adjective, dull, flat, lifeless, dreary) |
| obscure(adjective, dull, flat, boring, lifeless) |
| off(adjective, dull, moderate, low, slow) |
| on hold(expression, adjective, dull, idle, sluggish) |
| opiate(adjective, quiet, slow, heavy, sleepy) |
| oppressive(adjective, dull, unhappy, dark, gloomy) |
| ossified(adjective, dull, idle, sluggish, lazy) |
| out(adjective, dull, quiet, slow, heavy) |
| out of action(expression, adjective, idiom, dull, idle) |