wild man

noun4

1. •
   A mythic or legendary primitive man inhabiting forests or wilderness regions, typically depicted as hairy all over and unclothed.

   • He had rescued the duchess from the very fangs of the monster, which, he assured the ladies, was neither a wolf, nor a bear, nor yet a wild man of the woods. — 1820
2. •
   A rowdy, dissolute, rash, or violent man.

   • [H]e was a sinner, unregenerated, a wild man in her estimation, a being of quite another kind than herself. — 1879
3. •
   A man who advocates unorthodox or outrageous opinions or who behaves in an eccentric manner.

   • In popular lore, Feynman often comes off as the wild man of physics, throwing out one crazy idea after another in a frenzied search for truth. — 2011
4. •
   A representation of such a figure, usually shown as a club-bearing, hairy man of the woods.