Definition of xt:
(n) :
Abbreviation of extraterrestrial. [A being originating from outside of the Earth's atmosphere, from space, or from another planet; an alien.]
(n) :
(computing) Initialism of extended technology: a version of the IBM PC with a built-in hard drive, released in 1983.
(n) :
(uncommon, now archaic) Alternative form of X, abbreviation of Christ. [A placeholder for an unknown, suppressed or hypothetical name.]