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]