Source : Webster's Revised Unabridged Dictionary (1913)

Arborist \Ar"bor*ist\, n. [F. arboriste, fr. L. arbor tree.]
   One who makes trees his study, or who is versed in the
   knowledge of trees. --Howell.

Source : WordNet®

arborist
     n : a specialist in treating damaged trees [syn: {tree surgeon}]