How do you spell Marl

Available Definitions:
1)  v. t. - To cover, as part of a rope, with marline, marking a pecular hitch at each turn to prevent unwinding.
2)  n. - 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 .
3)  n. - To overspread or manure with marl; as, to marl a field.