[n] the act of giving a false appearance; "his conformity was only pretending"
[n] the act of imitating the behavior of some situation or some process by means of something suitably analogous (especially for the purpose of study or personnel training)
[n] representation of something (sometimes on a smaller scale)
[n] (computer science) the technique of representing the real world by a computer program; "a simulation should imitate the internal processes and not merely the results of the thing being simulated"