The Collaborative International Dictionary of English v.0.48:

Approximative \Ap*prox"i*ma*tive\, a. [Cf. F. approximatif.]
   Approaching; approximate. -- Ap*prox"i*ma*tive*ly, adv. --
   Ap*prox"i*ma*tive*ness, n.
   [1913 Webster]