Source : Webster's Revised Unabridged Dictionary (1913)

Marline \Mar"line\, n. [LG. marlien, marling, or D. marling,
   marlijn, fr. D. marren to tie, prob. akin to E. moor, v., and
   lijn line: cf.F. merlin. See {Moor}, v., {Line}.] (Naut.)
   A small line composed of two strands a little twisted, used
   for winding around ropes and cables, to prevent their being
   weakened by fretting.

   {Marline spike}, {Marling spike} (Naut.), an iron tool
      tapering to a point, used to separate the strands of a
      rope in splicing and in marling. It has an eye in the
      thick end to which a lanyard is attached. See {Fid}.
      [Written also {marlin spike}]

   {Marline-spike bird}. [The name alludes to the long middle
      tail feathers.] (Zo["o]l.)
   (a) A tropic bird.
   (b) A jager, or skua gull.

Marline \Mar"line\, v. t. [F. merliner.] (Naut.)
   To wind marline around; as, to marline a rope.

Source : WordNet®

marline
     n : a small usually tarred line of 2 strands