rud·dle (rŭd'l) n. Red ocherous iron ore, used in dyeing and marking. tr.v.
rud·dled also red·dled or rad·dled, rud·dling also red·dling or rad·dl·ing, rud·dles also red·dles or rad·dles To dye or mark with or as if with red ocher: ruddle sheep.
[Probably diminutive of rud, red, from Middle English rudde, from Old English rudu; see reudh- in Indo-European roots.]