The term "skinny-sissy" in a porn video tag refers to a specific type of content featuring a male character who is both slim or skinny, and exhibits sissy behavior. This type of video often includes scenes where the slim male character is humiliated, submissive, or engaged in feminine activities, usually for the purpose of humiliation or as part of dominance and submission role-play. The focus of this tag is on the physical appearance (skinny) and the behavioral aspect (sissy), targeting individuals who enjoy such specific niche content.