The Collaborative International Dictionary of English v.0.48:

Indissolvable \In`dis*solv"a*ble\, a. [Pref. in- not +
   dissolvable. Cf. Indissoluble.]
   Not dissolvable; incapable of being dissolved or separated;
   incapable of separation; perpetually firm and binding;
   indissoluble; as, an indissolvable bond of union. --Bp.
   Warburton.
   [1913 Webster]