The Collaborative International Dictionary of English v.0.48:

Patch \Patch\, n. [OE. pacche; of uncertain origin, perh. for
   placche; cf. Prov. E. platch patch, LG. plakk, plakke.]
   1. A piece of cloth, or other suitable material, sewed or
      otherwise fixed upon a garment to repair or strengthen it,
      esp. upon an old garment to cover a hole.
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            Patches set upon a little breach.     --Shak.
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   2. Hence: A small piece of anything used to repair a breach;
      as, a patch on a kettle, a roof, etc.
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   3. A small piece of black silk stuck on the face, or neck, to
      hide a defect, or to heighten beauty.
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            Your black patches you wear variously. --Beau. & Fl.
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   4. (Gun.) A piece of greased cloth or leather used as
      wrapping for a rifle ball, to make it fit the bore.
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   5. Fig.: Anything regarded as a patch; a small piece of
      ground; a tract; a plot; as, scattered patches of trees or
      growing corn.
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            Employed about this patch of ground.  --Bunyan.
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   6. (Mil.) A block on the muzzle of a gun, to do away with the
      effect of dispart, in sighting.
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   7. A paltry fellow; a rogue; a ninny; a fool. [Obs. or
      Colloq.] "Thou scurvy patch." --Shak.
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   Patch ice, ice in overlapping pieces in the sea.

   Soft patch, a patch for covering a crack in a metallic
      vessel, as a steam boiler, consisting of soft material, as
      putty, covered and held in place by a plate bolted or
      riveted fast.
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