simulation

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The act or process of simulating.
• noun An imitation; a sham.
• noun Assumption of a false appearance.
• noun Imitation or representation, as of a potential situation or in experimental testing.
• noun Representation of the operation or features of one process or system through the use of another.

from The Century Dictionary.

• noun The act of simulating, or feigning or counterfeiting; the false assumption of a certain appearance or character; pretense, usually for the purpose of deceiving.
• noun Specifically— In phonology, imitation in form; the alteration of the form of a word so as to approach or agree with that of another word having some accidental similarity, and to suggest a connection between them: a tendency of popular etymology.
• noun In biology, unconscious imitation or protective mimicry; assimilation in appearance.
• noun Resemblance; similarity.
• noun In French law, a fictitious engagement, contract, or conveyance, made eitner as a fraud where no real transaction is intended, or as a mask or cover for a different transaction, in which case it may sometimes be made in good faith and valid.

from the GNU version of the Collaborative International Dictionary of English.

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

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Something which simulates a system or environment in order to predict actual behaviour.
• noun The process of simulating.
• noun Assuming an appearance which is feigned, or not true.
• noun soccer The act of falling over in order to be awarded a foul, when a foul hasn't been committed.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the act of giving a false appearance
• noun 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 representation of something (sometimes on a smaller scale)
• noun (computer science) the technique of representing the real world by a computer program