A verb for “to cut, cleave”. Its root √KIR is well established and has the same basic meaning (PE17/73; Ety/KIR). In notes for drafts of the Earendel (Poem) from around 1930, ᴱQ. kiri- was glossed “cleave” (PE16/100), and its past form was used in this sense in the finished version of the poem as part of the phrase langon veakiryo kírier “the throat of the sea-ship clove [the waters]” (MC/216). The best evidence for its meaning “cut” in later notes is in the pair of prefixed verbs aucir- and hócir- “cut off” in the Quendi and Eldar essay from 1959-60 (WJ/365, 368).
This verb also appeared in the versions of the Markirya poem from the 1960s in the phrase métima hrestallo círa “leave the last shore” (MC/221). Helge Fauskanger suggested that in this context it might mean “sail” as in “✱cut through the water” (AL/Markirya, QQ/círa). However, I think the intended meaning is actually “leave = cleave (from)”, in combination with ablative hrestallo “[from] the last shore”.
Neo-Quenya: Based on the above, I think cir- has the connotation of “cut [completely]”, so as to cleave apart the thing cut, as opposed to rista- “cut [into]”. As such I think cir- can also be used metaphorically to mean “✱separate from” when combined with the ablative.
#cir-, see círa