The porn video tag "tranny-tits" is a combination of two words: "tranny" and "tits". In the context of adult content, the word "tranny" is often used as a shorthand for "transgender." Therefore, this tag would refer to transgender individuals with large or prominent breasts.
The term "tits" is slang for female breasts, which are often shown and touched in explicit adult content. Thus, the meaning of "tranny-tits" can be understood as adult video content featuring transgender individuals with large or prominent breasts. This tag is meant to appeal to viewers who are interested in these specific characteristics.