The Collaborative International Dictionary of English v.0.48:

Indissoluble \In*dis"so*lu*ble\, a. [L. indissolubilis: cf. F.
   indissoluble. See In- not, and Dissoluble, and cf.
   Indissolvable.]
   [1913 Webster]
   1. Not dissoluble; not capable of being dissolved, melted, or
      liquefied; insoluble; as, few substances are indissoluble
      by heat, but many are indissoluble in water. --Boyle.
      [1913 Webster]

   2. Incapable of being rightfully broken or dissolved;
      perpetually binding or obligatory; firm; stable, as, an
      indissoluble league or covenant.
      [1913 Webster]

            To the which my duties
            Are with a most indissoluble tie
            Forever knit.                         --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

indissoluble
    adj 1: (of a substance) incapable of being dissolved [syn:
           insoluble, indissoluble] [ant: soluble]
    2: used of decisions and contracts