The Collaborative International Dictionary of English v.0.48:

Instrumentality \In`stru*men*tal"i*ty\, n.; pl.
   Instrumentalities.
   The quality or condition of being instrumental; that which is
   instrumental; anything used as a means; medium; agency.
   [1913 Webster]

         The instrumentality of faith in justification. --Bp.
                                                  Burnet.
   [1913 Webster]

         The discovery of gunpowder developed the science of
         attack and defense in a new instrumentality. --J. H.
                                                  Newman.
   [1913 Webster]

WordNet (r) 3.0 (2006):

instrumentality
    n 1: a subsidiary organ of government created for a special
         purpose; "are the judicial instrumentalities of local
         governments adequate?"; "he studied the French
         instrumentalities for law enforcement"
    2: the quality of being instrumental for some purpose
    3: an artifact (or system of artifacts) that is instrumental in
       accomplishing some end [syn: instrumentality,
       instrumentation]