A naive or innocent person; a person who is fond of the outdoors; a boy or man who lives a healthy and athletic life in the countryside; (hence) a yokel, a rough or crude person.
Origin
1940s.
Definition of nature boy in US English:
nature boy
noun
US informal
A naive or innocent person; a person who is fond of the outdoors; a boy or man who lives a healthy and athletic life in the countryside; (hence) a yokel, a rough or crude person.