The Collaborative International Dictionary of English v.0.48:

XT \XT\, n. (Electronics)
   An abbreviation for crosstalk, the presence of an unwanted
   signal via an accidental coupling. [abbrev.]

   Syn: crosstalk.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

XT
    n 1: the presence of an unwanted signal via an accidental
         coupling [syn: crosstalk, XT]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

XT
       eXtended Technology (IBM, PC)


V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

XT
       eXtreme Tailoring (XP)


The Free On-line Dictionary of Computing (30 December 2018):

IBM PC XT
XT

    An IBM PC with a (slow) hard disk.  The XT was
   released in March 1983.  It had an Intel 8088 CPU.  The
   XT/370, released in October 1983, added IBM 370 mainframe
   emulation, and the XT 286 followed in September 1986 with an
   Intel 80286 CPU [Why?].

   (1996-05-21)


The Free On-line Dictionary of Computing (30 December 2018):

Xt

   The intrinsics of the X Window System Toolkit.

   [What does that mean?]