[1] : The Collaborative International Dictionary of English v.0.48

greensand \green"sand`\ -sa^nd`, n. geol.
   a variety of sandstone, usually imperfectly consolidated,
   consisting largely of glauconite, a silicate of iron and
   potash of a green color, mixed with sand and a trace of
   phosphate of lime.
   1913 webster

   note: handgreensand is often called marl, because it is a
         useful fertilizer. the greensand beds of the american
         cretaceous belong mostly to the upper cretaceous.
         1913 webster
see also:
marl 

[2] : The Collaborative International Dictionary of English v.0.48

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.
   1913 webster

   marling spike. naut. see under marline.
      1913 webster
see also:
marline marling spike 

[3] : The Collaborative International Dictionary of English v.0.48

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 terrae galli et britanni margam vocant."
   root274.
   a mixed earthy substance, consisting of carbonate of lime,
   clay, and sand, in very variable proportions, and accordingly
   designated as calcareous, clayey, or sandy. see greensand.
   1913 webster
see also:
greensand 

[4] : The Collaborative International Dictionary of English v.0.48

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.
   1913 webster
see also:
marled marling marl 

[5] : WordNet (r) 2.0

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

Marl >> M Words
Marl, definition of term: Marl
marl_pag1.html