Source : Webster's Revised Unabridged Dictionary (1913)

Abstractionist \Ab*strac"tion*ist\, n.
   An idealist. --Emerson.

Source : WordNet®

abstractionist
     adj : not representing or imitating external reality or the
           objects of nature; "a large abstract painting" [syn: {abstract},
            {nonfigurative}, {nonobjective}]
     n : a painter of abstract pictures [syn: {abstract artist}]