Source : Webster's Revised Unabridged Dictionary (1913)

Impressionistic \Im*pres`sion*is"tic\, a.
   Pertaining to, or characterized by, impressionism.

Source : WordNet®

impressionistic
     adj 1: of or relating to or based on an impression rather than on
            facts or reasoning; "a surprisingly impressionistic
            review bearing marks of hasty composition"; "she had
            impressionistic memories of her childhood"
     2: relating to or characteristic of impressionism;
        "impressionist music" [syn: {impressionist}]