A neologism for “undermine, weaken, hinder, sabotage, sap” coined by Röandil posted on 2023-04-09 in the Vinyë Lambengolmor Discord Server (VLDS), a combination of Q. nu “under” and ✶ñgwar- “fret”, so more literally “under-fret”.
Quenya
sap-
verb. dig
sap-
verb. to dig
(n)ungwar-
verb. to undermine, weaken, hinder, sabotage, sap, (lit.) to under/down-fret
sap- or sapa- vb. "dig", pa.t. sampë (PE16:145, QL:82); cf. sampa, and sapsanta below.