nuquerna adj. "reversed", or perhaps rather *"turned upside down". Attested in the phrases silmë nuquerna and árë nuquerna, q.v.
Quenya
nuquerna
adjective. reversed, inverted, *(lit.) under-turned
nuquerna
reversed
quer-
turn
#quer- vb. "turn" (transitive), attested as pa.t. quernë (VT49:18-20). Compare kuere (kwere) as one variant of a stem meaning "turn" (PE14:65). English intransitive "to turn" requires a reflexive pronoun in Quenya: mo quernë immo "one turned oneself" (VT49:6), in idiomatic English simply "one turned". Passive participle #querna "turned", isolated from nuquerna (q.v.) "under-turned" = reversed, turned upside down. Also in númenquerna "turned westward" (VT49:18), nanquernë "turned back", pl. form of *nanquerna (VT49:17-18, 20)
A word meaning “reversed” (LotR/1123) or “inverted” (PE22/49) in the names of the tengwar árë nuquerna and silmë nuquerna. It appears to be a combination of nu “under” and an adjectival form querna of the verb quer- “turn”, so more literally “✱under-turned”. Thus it only means “reversed” in a vertical direction, and “inverted” is a more accurate translation.