WordNet sense 1 (pretending with intention to deceive):

feigning, dissembling, pretence

WordNet sense 2 (imaginative intellectual play):

make-believe

WordNet sense 3 (a false or unsupportable quality):

pretension

WordNet sense 4 (an artful or simulated semblance):

guise, pretext

WordNet sense 5 (the act of giving a false appearance):

simulation, pretending