The Collaborative International Dictionary of English v.0.48:

Pretext \Pre"text\ (?; 277), n. [F. pr['e]texte, L. praetextum,
   fr. praetextus, p. p. of praetexere to weave before, allege
   as an excuse; prae before + texere to weave. See Text.]
   Ostensible reason or motive assigned or assumed as a color or
   cover for the real reason or motive; pretense; disguise.
   [1913 Webster]

         They suck the blood of those they depend on, under a
         pretext of service and kindness.         --L'Estrange.
   [1913 Webster]

         With how much or how little pretext of reason. --Dr. H.
                                                  More.
   [1913 Webster]

   Syn: Pretense; excuse; semblance; disguise; appearance. See
        Pretense.
        [1913 Webster]

WordNet (r) 3.0 (2006):

pretext
    n 1: something serving to conceal plans; a fictitious reason
         that is concocted in order to conceal the real reason [syn:
         pretext, stalking-horse]
    2: an artful or simulated semblance; "under the guise of
       friendship he betrayed them" [syn: guise, pretense,
       pretence, pretext]

Moby Thesaurus II by Grady Ward, 1.0:

94 Moby Thesaurus words for "pretext":
   acting, affectation, alibi, allege, alternative, appearance,
   attitudinizing, avow, bluff, bluffing, camouflage, cheating,
   choice, claim, cloak, color, coloring, cover, cover story,
   deception, delusion, disguise, dissemblance, dissembling,
   dissimulation, escape clause, escape hatch, excuse, explanation,
   facade, face, fakery, faking, false air, false front, false show,
   falsity, feigning, feint, four-flushing, fraud, front, gilt, gloss,
   guise, humbug, humbuggery, imposture, loophole, masquerade,
   meretriciousness, ostentation, outward show, playacting, plea,
   pose, posing, posture, pretend, pretense, pretension, profess,
   protest too much, purport, rational ground, rationale,
   rationalization, reason, reason for, reason why, red herring,
   representation, right, ruse, saving clause, seeming, semblance,
   sham, show, simulacrum, simulation, speciousness, stated cause,
   the big idea, the idea, the whatfor, the wherefore, the why,
   underlying reason, varnish, veil, way of escape, way out,
   window dressing



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

PRETEXT. The reasons assigned to justify an act, which have only the
appearance of truth, and which are without foundation; or which if true are
not the true reasons for such act. Vattel, liv. 3, c. 3, 32.