"Str8-fucks-tranny" is a porn video tag describing a specific type of content. In this case, the tag can be broken down into three parts:
1. Str8 - This refers to straight sex or heterosexual interactions between participants.
2. Fucks - This is a term used for the act of sexual intercourse, specifically penetration in this context.
3. Tranny - This term has evolved over time and can be considered outdated or politically incorrect by some, but generally refers to a transgender individual, typically a trans woman.
So, the tag "Str8-fucks-tranny" is describing a porn video where a heterosexual (straight) person engages in penetrative sex with a transgender individual (trans woman).