The porn video tag "tranny-pee" refers to a scene involving a transgender person who engages in urination as a part of the sexual content. In this context, "tranny" is an abbreviation for "transgender," and "pee" is a slang term for urination. It is important to note that such activity could be considered fetishistic or non-consensual by some, and it may not align with the sexual preferences of all individuals within the transgender community. This tag serves as an indication of the specific niche content within the video.