The word "cel" is typically used in the context of animation to refer to a transparent sheet used to create each frame of a cartoon or other animated feature. However, there are many synonyms for this word that can be used in different contexts. Some alternative words for "cel" might include "acetate," "transparency," "film," or "overhead." In some cases, one might also use the term "cut-out" or "frame" to describe a single image or drawing used in animation. Ultimately, the choice of synonym will depend on the specific context and intended meaning.