This is a designation earned by any person who has hiked the official (white blazed) Appalachian Trail in its entirety, between Springer Mountain in Georgia and Mount Katahdin in Maine's Baxter State Park.
The term is used as a matter of tradition (the original estimated length of the AT) and for continuity (rather than changing the designation each time the trail has a length adjustment when it is rerouted, which is pretty often).
Those who claim 2000-miler status should have hiked every mile of the AT between its termini, not just any 2000 miles.
The sequence, direction, speed, or length of time in which each section is traversed and whether one carries a pack or not don't matter, but only covering the entire trail counts, even for those who decide to hike the trail backwards, or sideways. Yes, equal recognition is given to thru-hikers and section hikers alike.
Example: Ed's a "2000 Miler". He hiked the whole trail.
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