The Collaborative International Dictionary of English v.0.48:

Mump \Mump\, v. i. [Akin to mumble; cf. D. mompen to cheat;
   perh. orig., to whine like a beggar, D. mompelen to mumble.
   See Mumble, Mum, and cf. Mumps.]
   1. To move the lips with the mouth closed; to mumble, as in
      sulkiness.
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            He mumps, and lovers, and hangs the lip. --Taylor,
                                                  1630.
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   2. To talk imperfectly, brokenly, or feebly; to chatter
      unintelligibly.
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   3. To cheat; to deceive; to play the beggar.
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            And then when mumping with a sore leg, . . . canting
            and whining.                          --Burke.
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   4. To be sullen or sulky. [Prov. Eng.]
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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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