illusion

[1]	deception , semblance , delusion , fancy , misconception , misapprehension , fallacy , error , mistake , mistaken/false impression
[2]	fantasy , fantasy , phantasy , day-dream , hallucination , fancy , phantasm , phantom , chimera , phantasmagoria , mirage , aberration , vision , spectre , figment of the imagination , will-o'-the-wisp , ignis fatuus
[3]	delusion , head game
[4]	magic trick , conjuring trick , trick , magic , legerdemain , conjuration , thaumaturgy , deception