From The Collaborative International Dictionary of English v.0.48:
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. [1913 Webster]
2. To injure or destroy, as a steamboat or other vessel, by a snag, or projecting part of a sunken tree. [U. S.] [1913 Webster]
From 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. [1913 Webster]
The coat of arms Now on a naked snag in triumph borne. --Dryden. [1913 Webster]
2. A tooth projecting beyond the rest; contemptuously, a broken or decayed tooth. --Prior. [1913 Webster]
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. [1913 Webster]
4. (Zool.) One of the secondary branches of an antler. [1913 Webster] [1913 Webster]
Snag boat, a steamboat fitted with apparatus for removing snags and other obstructions in navigable streams. [U.S.]
Snag tooth. Same as Snag, 2. [1913 Webster]
How thy snag teeth stand orderly, Like stakes which strut by the water side. --J. Cotgrave. [1913 Webster]