A large area of unmodified or slightly modified land, and/or sea, retaining its natural character and influence, without permanent or significant habitation.

Dudley, N. (ed.) IUCN 2008 1

An area where the earth and its community of life are untrammeled by man, where man himself is a visitor who does not remain. An area of wilderness is further defined to mean an area of undeveloped Federal land retaining its primeval character and influence, without permanent improvements or human habitation, which is protected and managed so as to preserve its natural conditions and which:

  1. generally appears to have been affected primarily by the forces of nature, with the imprint of man's work substantially unnoticeable;
  2. has outstanding opportunities for solitude or a primitive and unconfined type of recreation;
  3. has at least five thousand acres of land or is of sufficient size as to make practicable its preservation and use in an unimpaired condition; and
  4. may also contain ecological, geological, or other features of scientific, educational, scenic, or historical value.

The U.S. Wilderness Act, 1964 2