Source : Webster's Revised Unabridged Dictionary (1913)

Irremovable \Ir`re*mov"a*ble\, a.
   Not removable; immovable; inflexible. --Shak. --
   {Ir`re*mov"a*bly}, adv.

Source : WordNet®

irremovable
     adj : impossible to remove or take away or dismiss; "irremovable
           boulders"; "irremovable obstacles" [ant: {removable}]