WordWeb Online

1. (of liquids) clouded as with sediment
   "murky waters";
   - cloudy, muddy, mirky [archaic], turbid
    
2. Dark or gloomy
   "murky rooms lit by smoke-blackened lamps"; "a murky dungeon";
   - mirky [archaic]
    
3. Deliberately unclear; unclear in a dishonest or bad way

Derived forms: murkiest, murkier

See also: opaque, shaded