Take it from the top...definitions: SNAG

snag is:
(Noun)
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.

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. One of the secondary branches of an antler. Snag boat, a steamboat fitted with apparatus for removing snags and other obstructions in navigable streams. Snag tooth. Same as Snag. "How thy snag teeth stand orderly, Like stakes which strut by the water side." (J. Cotgrave)

Verb
1. To cut the snags or branches from, as the stem of a tree; to hew roughly.
2. To injure or destroy, as a steamboat or other vessel, by a snag, or projecting part of a sunken tree.
3. To obtain by a quick action, as though by snagging something passing by; often used of an opportunistic or fortunate action.

Origin: Snagged; Snagging.

Source: Websters Dictionary

Additional sources:
snag
Noun
A rough, sharp, or jagged protuberance, as:
A tree or a part of a tree that protrudes above the surface in a body of water. Also called sawyer. See Regional Note at preacher.
A snaggletooth.
A break, pull, or tear in fabric.
An unforeseen or hidden obstacle. See Synonyms at obstacle.
A short or imperfectly developed branch of a deer's antler.

Verb
To tear, break, hinder, or destroy by or as if by a snag: snagged a stocking on a splinter.
Informal. To catch unexpectedly and quickly: snagged a bargain.
To free of snags: snagged the river.
To catch (a fish), especially by hooking in a place other than its mouth.