Source : Webster's Revised Unabridged Dictionary (1913)

Coextensive \Co`ex*ten"sive\, a.
   Equally extensive; having equal extent; as, consciousness and
   knowledge are coextensive. --Sir W. Hamilton. --
   {Co`ex*ten"sive*ly}, adv. -- Co`ex*ten"sive*ness, n.

Source : WordNet®

coextensive
     adj : of equal extent or scope or duration [syn: {coterminous}, {conterminous}]