Snarled things are tangled or matted, like your cat's snarled fur or the snarled raspberry bushes in your yard.
When something's literally tied in knots, it's snarled. Long, snarled hair is hard to comb through, and snarled shoelaces can slow down even the most energetic kindergartener. It works figuratively, too, when things are impeded or stuck: "The snarled traffic made her an hour late to her meeting." Snarled probably comes from snare and its Scandinavian root meaning "twisted cord."