The Etymologies seem to list this word as a noun, but it is clearly the third person singular of the verb
Noldorin
osgar
verb. (he) cuts, amputates
osgar-
verb. to cut round, amputate
osgar-
verb. to cut round, to amputate
blâb
verb. (he) flaps, beats
lhammas
noun. account of tongues
lhâf
verb. (he) licks
lhôd
verb. (he) floats
orthor
verb. (he) masters, conquers
rhest
noun. cut
rhest
noun. cut
rhista-
verb. to cut
rhista-
verb. to rend, rip
síla
verb. (he) shines white
sôg
verb. (he) drinks
thia
verb. it appears
tôg
verb. (he) leads, brings
tôl
verb. (he) comes
According to WJ/301, the expression tôl acharn "vengeance comes" was later changed to tûl acharn by Tolkien
A verb in The Etymologies of the 1930s appearing in its Noldorin-style infinitive form esgeri “cut round, amputate” and 3rd. sg. osgar under the root ᴹ√OS “round, about” (Ety/OS). It is a combination of N. os- “about” and N. ✱car- “do, make”, so literally means “✱make round/about”. Its inflected present tense forms would still have i-affection in Sindarin, as in ✱esgerin “I cut round, I amputate”.