The act of impersonating a program or machine for the purposes of deceiving another party. This technique exploits people's blind trust in technology and is a test only because it challenges the intelligence of the supposed second party.
For example, in bad sitcoms people often attempt to impersonate a answering machine to avoid a telephone conversation with someone they dislike, often with 'hilarious consequences'. I've never seen this work in real life but it could, hypothetically.
This is also a technique used by some crackera to socially engineer dumb users.