rissë noun? The word is not clearly glossed but apparently means "cut" or "cleft" (ravine), the cognate of the final element of Imladris, Sindarin name of Rivendell. (PE17:87)
Quenya
hyar-
cleave
hyar-
verb. cleave
rissë
cut
rista
cut
rista (2) noun "cut" (RIS), cf. #1 above.
#hyar- vb. "cleave" (1st pers. aorist hyarin "I cleave") (SYAD). Pa.t. probably *hyandë since the R of hyar- was originally D; cf. rer- "sow", pa.t. rendë, from the root RED.