The reading of the gloss is uncertain
Noldorin
rant
noun. lode, vein
rant
noun. lode, vein
rant
noun. course, riverbed
rath
noun. course, riverbed
rath
noun. street (in a city)
cû
noun. arch, crescent
cû
noun. bow
iôr
noun. course
iôr
noun. course
rhib-
verb. to flow like a (torrent ?)
siria-
verb. to flow
A noun in The Etymologies of the 1930s glossed “course” derived from ON. yura under the root ᴹ√YUR “run” (Ety/YUR).