Trance is a state of semi-consciousness in which a person is not self-aware and is either altogether unresponsive to external stimuli (but nevertheless capable of pursuing and realizing an aim) or is selectively responsive in following the directions of the person (if any) who has induced the trance. Trance states may occur involuntarily and unbidden.
The term trance may be associated with hypnosis, meditation, magic, flow, prayer, and altered states of consciousness.
Trance in its modern meaning comes from an earlier meaning of "a dazed, half-conscious or insensible condition or state of fear", via the Old French transe "fear of evil", from the Latin transīre "to cross", "pass over".
Source: Wikipedia