The Collaborative International Dictionary of English v.0.48:

Fang \Fang\, n. [From Fang, v. t.; cf. AS. fang a taking,
   booty, G. fang.]
   1. (Zool.) The tusk of an animal, by which the prey is seized
      and held or torn; a long pointed tooth; esp., one of the
      usually erectile, venomous teeth of serpents. Also, one of
      the falcers of a spider.
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            Since I am a dog, beware my fangs.    --Shak.
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   2. Any shoot or other thing by which hold is taken.
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            The protuberant fangs of the yucca.   --Evelyn.
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   3. (Anat.) The root, or one of the branches of the root, of a
      tooth. See Tooth.
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   4. (Mining) A niche in the side of an adit or shaft, for an
      air course. --Knight.
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   5. (Mech.) A projecting tooth or prong, as in a part of a
      lock, or the plate of a belt clamp, or the end of a tool,
      as a chisel, where it enters the handle.
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   6. (Naut.)
      (a) The valve of a pump box.
      (b) A bend or loop of a rope.
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   In a fang, fast entangled.

   To lose the fang, said of a pump when the water has gone
      out; hence:

   To fang a pump, to supply it with the water necessary to
      make it operate. [Scot.]
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