naturist

Short definition from Wiktionary

Noun

1. 1
   One who follows a philosophical belief in a naked, natural life and prefers to live without clothes, often for reasons of ecology, health, religious belief, and/or ethical concerns.
2. 2
   One who believes in the doctrine of naturism, which attributes everything to nature.

Adjective

1. 1
   Of or relating to naturism, the philosophical belief in a naked, natural life and prefers to live without clothes, often for reasons of health, ecology, religious belief, and/or ethical concerns.
2. 2
   Relating to or believing in the doctrine of naturism, which attributes everything to nature.