Nature, noun

1. the material world, esp. as surrounding humankind and existing independently of human activities.
2. the natural world as it exists without human beings or civilization.
3. the elements of the natural world, as mountains, trees, animals, or rivers.
4. natural scenery.
5. the universe, with all its phenomena.
6. the sum total of the forces at work throughout the universe.
7. reality, as distinguished from any effect of art: a portrait true to nature.
8. the particular combination of qualities belonging to a person, animal, thing, or class by birth, origin, or constitution; native or inherent character: human nature.
9. the instincts or inherent tendencies directing conduct: a man of good nature.
12. the original, natural, uncivilized condition of humankind.
14. a primitive, wild condition; an uncultivated state.
15. a simple, uncluttered mode of life without the conveniences or distractions of civilization: a return to nature.
19. in a state of nature,
a. in an uncivilized or uncultured condition.
b. without clothes; nude; naked.

* Excerpted from the Random House Webster's Unabridged Dictionary 3.0.