dissimulator

from WordNet (r) 3.0 (2006)

dissimulator
    n 1: a person who professes beliefs and opinions that he or she
         does not hold in order to conceal his or her real feelings
         or motives [syn: {hypocrite}, {dissembler}, {dissimulator},
         {phony}, {phoney}, {pretender}]

from The Collaborative International Dictionary of English v.0.48

Dissimulator \Dis*sim"u*la`tor\, n. [L.]
   One who dissimulates; a dissembler.
   [1913 Webster]