The Collaborative International Dictionary of English v.0.48:

Purl \Purl\, v. i. [imp. & p. p. Purled; p. pr. & vb. n.
   Purling.] [Cf. Sw. porla, and E. pur to murmur as a cat.]
   1. To run swiftly round, as a small stream flowing among
      stones or other obstructions; to eddy; also, to make a
      murmuring sound, as water does in running over or through
      obstructions.
      [1913 Webster]

            Swift o'er the rolling pebbles, down the hills,
            Louder and louder purl the falling rills. --Pope.
      [1913 Webster]

   2. [Perh. fr. F. perler to pearl, to bead. See Pearl, v. &
      n.] To rise in circles, ripples, or undulations; to curl;
      to mantle.
      [1913 Webster]

            thin winding breath which purled up to the sky.
                                                  --Shak.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Purling \Purl"ing\, n. [See 3d Purl.]
   The motion of a small stream running among obstructions;
   also, the murmur it makes in so doing.
   [1913 Webster]