1. An early theatre, mainly circa 1903-1914, which charged 5 cents admission. Nickelodeon = nickel + odeon (the Greek word for theatre). * Synonym: nickelodeon theatre. 2. Term used to describe a coin-operated piano, orchestrion, or similar instrument. (Modern usage; never used by the manufacturers. Such instruments originally were called electric pianos, orchestrions, etc. The nickelodeon term has become very popular and is in wide use among collectors and the public today.)