Source : Webster's Revised Unabridged Dictionary (1913)

Obsolesce \Ob`so*lesce"\, v. i. [L. obsolescere. See
   {Obsolescent}.]
   To become obsolescent. [R.] --Fitzed. Hall.

Source : WordNet®

obsolesce
     v : become obsolete, fall into disuse; "This word has not
         obsolesced, although it is rarely used"