[1] : The Collaborative International Dictionary of English v.0.48

treason \trea"son\, n. oe. tresun, treisun, traisoun, of.
   tra"ison, f. trahison, l. traditio a giving up, a
   delivering up, fr. tradere to give up, betray. see traitor,
   and cf. tradition.
   1. the offense of attempting to overthrow the government of
      the state to which the offender owes allegiance, or of
      betraying the state into the hands of a foreign power;
      disloyalty; treachery.
      1913 webster

            the treason of the murthering in the bed. --chaucer.
      1913 webster

   note: in monarchies, the killing of the sovereign, or an
         attempt to take his life, is treason. in england, to
         imagine or compass the death of the king, or of the
         queen consort, or of the heir apparent to the crown, is
         high treason, as are many other offenses created by
         statute. in the united states, treason is confined to
         the actual levying of war against the united states, or
         to an adhering to their enemies, giving them aid and
         comfort.
         1913 webster

   2. loosely, the betrayal of any trust or confidence;
      treachery; perfidy.
      1913 webster

            if he be false, she shall his treason see.
                                                  --chaucer.
      1913 webster

   petit treason. see under petit.
      1913 webster
see also:
traitor tradition petit treason petit 

[2] : WordNet (r) 2.0

treason
     n 1: a crime that undermines the offender's government syn: high
          treason, lese majesty
     2: disloyalty by virtue of subversive behavior syn: subversiveness,
         traitorousness
     3: an act of deliberate betrayal syn: treachery, betrayal,
         perfidy
see also:
high treason lese majesty subversiveness traitorousness treachery betrayal 
perfidy 

[3] : Moby Thesaurus II by Grady Ward, 1.0

47 moby thesaurus words for "treason":
   golconda, machiavellianism, apostasy, backsliding, betrayal, bolt,
   breach of trust, breakaway, collaboration, crossing-over, deceit,
   deceitfulness, defection, degeneration, desertion, disloyalty,
   duplicity, eldorado, faithlessness, fifth-column activity,
   fraternization, going over, gold mine, high treason, lese majesty,
   mine, misprision, misprision of treason, perfidiousness, perfidy,
   petty treason, quislingism, ratting, recidivation, recidivism,
   recreancy, renunciation, secession, sedition, seditiousness,
   treacherousness, treachery, treasure, treasure trove,
   treasure-house, treasury, turning traitor

[4] : Bouvier's Law Dictionary, Revised 6th Ed (1856)

treason, crim. law. this word imports a betraying, treachery, or breach of 
allegiance. 4 bl. com. 75. 
     2. the constitution of the united states, art. 3, s. 3, defines treason 
against the united states to consist only in levying war q.v. against 
them, or in adhering to their enemies, giving them aid or comfort. this 
offence is punished with death. act of april 30th, 1790, 1 story's laws u. 
s. 83. by the same article of the constitution, no person shall be convicted 
of treason, unless on the testimony of two witnesses to the same overt act, 
or on confession in open court. vide, generally, 3 story on the const. ch. 
39, p. 667; serg. on the const. ch. 30; united states v. fries, pamph.; 1 
tucker's blackst. comm. appen. 275, 276; 3 wils. law lect. 96 to 99; foster, 
disc. i; burr's trial; 4 cranch, r. 126, 469 to 508; 2 dall. r. 246; 355; 1 
dall. rep. 35; 3 wash. c. c. rep. 234; 1 john. rep. 553 11 johns. r. 549; 
com. dig. justices, k; 1 east, p. c. 37 to 158; 2 chit. crim. law, 60 to 
102; arch. cr. pl. 378 to 387. 

Treason >> T Words
Treason, definition of term: Treason
treason_pag1.html

High Treason >> H Words
High Treason, definition of term: High Treason
high+treason_pag1.html