Source : Webster's Revised Unabridged Dictionary (1913)

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.

            Let our wines, without mixture of stum, be all fine.
                                                  --B. Jonson.

            And with thy stum ferment their fainting cause.
                                                  --Dryden.

   2. Wine revived by new fermentation, reulting from the
      admixture of must. --Hudibras.

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.

         We stum our wines to renew their spirits. --Floyer.