marl

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A crumbly mixture of clays, calcium and magnesium carbonates, and remnants of shells that is sometimes found under desert sands and used as fertilizer for lime-deficient soils.
• transitive verb To fertilize with such a mixture.

from The Century Dictionary.

• To overspread or manure with marl.
• To wonder; marvel.
• noun A mixture of clay with carbonate of lime, the latter being present in considerable quantity, forming a mass which is not consolidated, but falls to pieces readily on exposure to the air.
• noun The fiber of those peacock-feathers which have the webs long and decomposed, so that the barbs stand apart, as if raveled: used for making artificial flies.
• See the quotation.
• Nautical, to wind, as a rope, with marline, spun-yarn, twine, or other small stuff, every turn being secured by a sort of hitch: a common method of fastening strips of canvas called parceling, to prevent chafing.
• To ravel, as silk.
• noun Marble.
• noun A marble (plaything).

from the GNU version of the Collaborative International Dictionary of English.

• transitive verb To overspread or manure with marl.
• transitive verb (Naut.) To cover, as part of a rope, with marline, marking a pecular hitch at each turn to prevent unwinding.
• transitive verb (Naut.) See under Marline.
• noun 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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A mixed earthy substance, consisting of carbonate of lime, clay, and possibly sand, in very variable proportions, and accordingly designated as calcareous, clayey, or sandy.
• verb To cover, as part of a rope, with marline, marking a peculiar hitch at each turn to prevent unwinding.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

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