The Collaborative International Dictionary of English v.0.48:

Frustrative \Frus"tra*tive\, a.
   Tending to defeat; fallacious. [Obs.] --Ainsworth.
   [1913 Webster]

WordNet (r) 3.0 (2006):

frustrative
    adj 1: preventing realization or attainment of a desire [syn:
           frustrating, frustrative, thwarting]