obsolescentEnglishOxford New American Dictionaryobsolescent /ˌäbsəˈles(ə)nt, ˌɑbsəˈlɛs(ə)nt / ▸ adjective becoming obsolete: the custom is now obsolescent. – ORIGIN mid 18th century : from Latin obsolescent- ‘falling into disuse’, from the verb obsolescere.