Celluloid/ˈseljulɔɪd/ Definition 1 of 2Pro Tip 1/3Historic Material Celluloid is an early form of plastic, indicating historic or vintage items when mentioned. They found reels of celluloid in the antique shop. Pro Tip 2/3Early Film Celluloid refers to a medium used in early photography and cinema. Classic films were often shot on celluloid strips. Pro Tip 3/3Flammability Warning Historical celluloid was highly flammable; context may imply risk or fragility. Store these celluloid items carefully to prevent fire.