The Collaborative International Dictionary of English v.0.48:

Mump \Mump\, v. t. [imp. & p. p. Mumped; p. pr. & vb. n.
   Mumping.]
   1. To utter imperfectly, brokenly, or feebly.
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            Old men who mump their passion.       --Goldsmith.
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   2. To work over with the mouth; to mumble; as, to mump food.
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   3. To deprive of (something) by cheating; to impose upon.
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