noun (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)(noun.act)

  source: wordnet30
• (computer science) the technique of representing the real world by a computer program(noun.cognition)

  Example:
  A simulation should imitate the internal processes and not merely the results of the thing being simulated.
  

  Synonym:
  computer simulation
  

  source: wordnet30
• representation of something (sometimes on a smaller scale)(noun.artifact)

  Synonym:
  model
  

  source: wordnet30
• the act of giving a false appearance(noun.act)

  Synonym:
  feigning, pretence, pretending, pretense
  

  source: wordnet30
• The act of simulating, or assuming an appearance which is feigned, or not true; -- distinguished from dissimulation, which disguises or conceals what is true.(noun)

  source: webster1913