The Collaborative International Dictionary of English v.0.48:

Stum \Stum\, n. [D. stom must, new wort, properly, dumb; cf. F.
   vin muet stum. Cf. Stammer, Stoom.]
   1. Unfermented grape juice or wine, often used to raise
      fermentation in dead or vapid wines; must.
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            Let our wines, without mixture of stum, be all fine.
                                                  --B. Jonson.
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            And with thy stum ferment their fainting cause.
                                                  --Dryden.
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   2. Wine revived by new fermentation, reulting from the
      admixture of must. --Hudibras.
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The Collaborative International Dictionary of English v.0.48:

Stum \Stum\, v. t. [imp. & p. p. Stummed; p. pr. & vb. n.
   Stumming.]
   To renew, as wine, by mixing must with it and raising a new
   fermentation.
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         We stum our wines to renew their spirits. --Floyer.
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