Source : Webster's Revised Unabridged Dictionary (1913)

Indestructible \In`de*struc"ti*ble\, a. [Pref. in- not +
   destructible: cf. F. indestructible.]
   Not destructible; incapable of decomposition or of being
   destroyed. -- {In`de*struc"ti*ble*ness}, n. --
   {In`de*struc"ti*bly}, adv.

Source : WordNet®

indestructible
     adj 1: not easily destroyed [ant: {destructible}]
     2: very long lasting; "less durable rocks were gradually worn
        away to form valleys"; "the perdurable granite of the
        ancient Appalachian spine of the continent" [syn: {durable},
         {perdurable}, {undestroyable}]