I need the vocab word for the following definiton:

Unrealistic devices or procedures that the audience agrees to accept (ex: aside).

http://www.google.com/search?hl=en&source=hp&biw=1366&bih=643&q=Unrealistic+devices+or+procedures+that+the+audience+agrees+to+accept&aq=f&aqi=&aql=&oq=