Learn how to say Dumbbell correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word dumb-bell:
1a short bar with a weight at each end, used typically in pairs for exercise or muscle-building.
[as modifier] shaped like a dumb-bell:
a dumb-bell molecule
2North American informal a stupid person.
early 18th century: originally denoting an apparatus similar to that used to ring a church bell (but without the bell, so noiseless or ‘dumb’); sense 2 (dating from the 1920s) is an extended use by association with dumb ‘stupid’