Dumb-bell :: Dumb-bell (n.) A weight, consisting of two spheres or spheroids, connected by a short bar for a handle; used (often in pairs) for gymnastic exercise..
Dumb-waiter :: Dumb-waiter (n.) A framework on which dishes, food, etc., are passed from one room or story of a house to another; a lift for dishes, etc.; also, a piece of furniture with movable or revolving shelves..
Dumbledor :: Dumbledor (n.) A bumblebee; also, a cockchafer..