There are several synonyms for the word "backflap" that can be used in different contexts. Some of the most common synonyms for this word include "rear flap," "flip side," "backside flap," and "reverse flap." These synonyms can be used when referring to the back panel or flap of a book cover, envelope, or jacket. Other synonyms for "backflap" may also include "back cover," "back page," or "inside back cover." Regardless of which synonym is used, the meaning is generally the same - a flap or panel located at the back of a document or packaging that can provide additional information or serve a specific purpose.