Source : Webster's Revised Unabridged Dictionary (1913)

Naturalist \Nat"u*ral*ist\, n. [Cf. F. naturaliste.]
   1. One versed in natural science; a student of natural
      history, esp. of the natural history of animals.

   2. One who holds or maintains the doctrine of naturalism in
      religion. --H. Bushnell.

Source : WordNet®

naturalist
     n 1: an advocate of the doctrine that the world can be understood
          in scientific terms
     2: a biologist knowledgeable about natural history (especially
        botany and zoology) [syn: {natural scientist}]