The Collaborative International Dictionary of English v.0.48:

Dupery \Dup"er*y\ (d[=u]p"[~e]r*[y^]), n. [F. duperie, fr.
   duper.]
   The act or practice of duping. [R.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

dupery
    n 1: something intended to deceive; deliberate trickery intended
         to gain an advantage [syn: fraud, fraudulence,
         dupery, hoax, humbug, put-on]