Source : Webster's Revised Unabridged Dictionary (1913)

Marl \Marl\, v. t. [See {Marline}.] (Naut.)
   To cover, as part of a rope, with marline, marking a pecular
   hitch at each turn to prevent unwinding.

   {Marling spike}. (Naut.) See under {Marline}.

Marl \Marl\, n. [OF. marle, F. marne, LL. margila, dim. of L.
   marga marl. Originally a Celtic word, according to Pliny,
   xvii. 7: ``Quod genus terr[ae] Galli et Britanni margam
   vocant.'' [root]274.]
   A mixed earthy substance, consisting of carbonate of lime,
   clay, and sand, in very varivble proportions, and accordingly
   designated as calcareous, clayey, or sandy. See {Greensand}.

Marl \Marl\, v. t. [imp. & p. p. {Marled}; p. pr. & vb. n.
   {Marling}.] [Cf. F. marner. See {Marl}, n.]
   To overspread or manure with marl; as, to marl a field.

Source : WordNet®

marl
     n : a loose and crumbling earthy deposit consisting mainly of
         calcite or dolomite; used as a fertilizer for soils
         deficient in lime