Wildfire

Wildfire is any fire started by an unplanned ignition caused by lightning; volcanoes; other acts of nature; unauthorized activity; or accidental, human-caused actions, or a prescribed fire that has developed into a wildfire. A wildfire that predominantly occurs on wildland is a natural event.

Source

40 CFR § 50.1

Scoping language

As used in this part, all terms not defined herein shall have the meaning given them by the Act.