obsolescent adj.

"that is no longer practiced or used, out of date, gone out of use, of a discarded type," 1570s, from Latin obsoletus "grown old, worn-out," past participle of obsolescere "fall into disuse, be forgotten about, become tarnished," which probably is from ob "away" (see ob-) + an expanded form of solere "to be used to, be accustomed" (see insolent).

"state or process of gradually falling into disuse, a becoming obsolete," 1809; see obsolescent + -ence. Phrase planned obsolescence was coined 1932, revived as a disparaging term 1950s.