A personal definition of atmospheric trance.
Atmospheric trance is, as the name suggests, atmospheric. Some people ignorantly group it together with uplifting "kiksutrance" (which is the "reach for the lasers and let those ecstasy pills peak" stuff). Atmospheric trance, in my opinion, is the true trance music due to its hypnotic nature (for a perfect example of what I mean, listen to Max Graham - Falling Together or, Moogwai - Labyrinth part 2).
Some characteristic elements include but are not limited to:
Examples of artists and tracks that I define as atmospheric trance: