The Collaborative International Dictionary of English v.0.48:

Tron \Tron\, n.
   See 3d Trone, 2. [Obs. or Scot.]
   [1913 Webster]

Jargon File (4.4.4, 14 Aug 2003):

tron
 v.

   [NRL, CMU; prob. fr. the movie Tron] To become inaccessible except
via
   email or talk(1), especially when one is normally available via
   telephone or in person. Frequently used in the past tense, as in:
"Ran
   seems to have tronned on us this week" or "Gee, Ran, glad you were
   able to un-tron yourself". One may also speak of tron mode; compare
   spod.

   Note that many dialects of BASIC have a TRON/TROFF command pair that
   enables/disables line number tracing; this has no obvious
relationship
   to the slang usage.


V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006):

TRON
       The Realtime Operating system Nucleus