The term ONE AT A MULTIPLEX can be summarized as a job that involves managing a single movie SCREEN at a multiplex theater. A multiplex theater is a large movie theater complex that typically has multiple screens and auditoriums, allowing for the simultaneous showing of multiple movies. The job of ONE AT A MULTIPLEX would involve overseeing the operations of one of these screens, including ticket sales, customer service, and ensuring the smooth running of the movie showings.