The Collaborative International Dictionary of English v.0.48:

Knap \Knap\, v. t. [imp. & p. p. Knapped; p. pr. & vb. n.
   Knapping.] [D. knappen to chew, bite, crack, take hold of;
   prob. of imitative origin.]
   1. To bite; to bite off; to break short. [Obs. or Prov. Eng.
      ]
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            He will knap the spears apieces with his teeth.
                                                  --Dr. H. More.
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            He breaketh the bow, and knappeth the spear in
            sunder.                               --Ps. xlvi. 9
                                                  (Book of
                                                  Common
                                                  Prayer.)
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   2. To strike smartly; to rap; to snap. [Chiefly Brit.]
      --Bacon.
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