The Collaborative International Dictionary of English v.0.48:

Snag \Snag\, n. [Prov. E., n., a lump on a tree where a branch
   has been cut off; v., to cut off the twigs and small branches
   from a tree, of Celtic origin; cf. Gael. snaigh, snaidh, to
   cut down, to prune, to sharpen, p. p. snaighte, snaidhte, cut
   off, lopped, Ir. snaigh a hewing, cutting.]
   1. A stump or base of a branch that has been lopped off; a
      short branch, or a sharp or rough branch; a knot; a
      protuberance.
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            The coat of arms
            Now on a naked snag in triumph borne. --Dryden.
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   2. A tooth projecting beyond the rest; contemptuously, a
      broken or decayed tooth. --Prior.
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   3. A tree, or a branch of a tree, fixed in the bottom of a
      river or other navigable water, and rising nearly or quite
      to the surface, by which boats are sometimes pierced and
      sunk.
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   4. (Zool.) One of the secondary branches of an antler.
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   Snag boat, a steamboat fitted with apparatus for removing
      snags and other obstructions in navigable streams. [U.S.]


   Snag tooth. Same as Snag, 2.
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            How thy snag teeth stand orderly,
            Like stakes which strut by the water side. --J.
                                                  Cotgrave.
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