Source : Webster's Revised Unabridged Dictionary (1913)

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.

            The coat of arms Now on a naked snag in triumph
            borne.                                --Dryden.

   2. A tooth projecting beyond the rest; contemptuously, a
      broken or decayed tooth. --Prior.

   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.

   4. (Zo["o]l.) One of the secondary branches of an antler.

Snag \Snag\, v. t. [imp. & p. p. {Snagged}; p. pr. & vb. n.
   {Snagging}.]
   1. To cut the snags or branches from, as the stem of a tree;
      to hew roughly. [Prov. Eng.] --Halliwell.

   2. To injure or destroy, as a steamboat or other vessel, by a
      snag, or projecting part of a sunken tree. [U. S.]

Source : WordNet®

snag
     n 1: a sharp protuberance
     2: a dead tree that is still standing, usually in an
        undisturbed forest; "a snag can provide food and a habitat
        for insects and birds"
     3: an opening made forcibly as by pulling apart; "there was a
        rip in his pants"; "she had snags in her stockings" [syn:
        {rip}, {rent}, {split}, {tear}]
     4: an unforeseen obstacle [syn: {hang-up}, {hitch}, {rub}]
     v 1: catch on a snag; "I snagged my stocking"
     2: get by acting quickly and smartly; "snag a bargain"
     3: hew jaggedly
     [also: {snagging}, {snagged}]

Source : Free On-Line Dictionary of Computing

snag
     
        {bug}