celluloid [from cellulose], transparent, colorless synthetic plastic made by treating cellulose nitrate with camphor and alcohol. Celluloid was the first important synthetic plastic and was widely used as a substitute for more expensive substances, such as ivory, amber, horn, and tortoiseshell. It is highly flammable and has been largely superseded by newer plastics with more desirable properties. It has been used for combs, brush handles, billiard balls, knife handles, buttons, and other useful objects.

Name for the first synthetic plastic material, developed in 1869. Made of a colloid of cellulose nitrate (nitrocellulose) plasticized with camphor, it is tough, cheap to produce, and resistant to water, oils, and dilute acids. It found a great variety of uses in combs, films, toys, and many other mass-produced consumer goods. Though it has been replaced in many uses by nonflammable synthetic polymers (originally cellulose acetate and Bakelite, then a host of others), it is still manufactured and used.

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