A coating of ice, as on grass and trees, formed when extremely cold water droplets freeze almost instantly on a cold surface.
A coating, as of mud or slime, likened to a frosty film: "A meal couldn't leave us feeling really full unless it laid down a rime of fat globules in our mouths and stomachs"(James Fallows).
tr.v.
rimed, rim·ing, rimes To cover with or as if with frost or ice: "heavy [shoes] rimed with mud and cement ... from the building site"(Seamus Deane).
[Middle English rim, from Old English hrīm.] rim'y adj.
[rahy-mee] 
mi