Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
exstinctĭo (ext-), ōnis, f. [exstinguo].
Prop., a putting out; trop., extinction, annihilation (very rare): supremus ille dies non exstinctionem sed commutationem affert loci, Cic. Tusc. 1, 49, 117: vitae, Cic. ap. Aug. de Trm. 14 fin. (Cic. Hortens. Fragm. 90).