- becoming obsolete; passing out of use, as a word: an obsolescent term.
- becoming outdated or outmoded, as machinery or weapons.
- Biology. gradually disappearing or imperfectly developed, as vestigial organs.
- becoming obsolete or out of date
adj.1755, from Latin obsolescentum (nominative obsolescens), present participle of obsolescere “fall into disuse” (see obsolete).