Definitions of snag:

• noun:   a dead tree that is still standing, usually in an undisturbed forest

  Example: "A snag can provide food and a habitat for insects and birds"

• noun:   a sharp protuberance
• noun:   an opening made forcibly as by pulling apart

  Example: "She had snags in her stockings"

• noun:   an unforeseen obstacle
• verb:   get by acting quickly and smartly

  Example: "Snag a bargain"

• verb:   hew jaggedly
• verb:   catch on a snag

  Example: "I snagged my stocking"