Definition of "Celluloid" :

noun: a medium that disseminates moving pictures

"Theater pieces transferred to celluloid."

noun: highly flammable substance made from cellulose nitrate and camphor; used in e.g. motion-picture and X-ray film; its use has decreased with the development of nonflammable thermoplastics

adjective: artificial as if portrayed in a film

"A novel with flat celluloid characters."