"FTM" stands for "Female to Male," which refers to a transgender person who was assigned female at birth but identifies as male. In this context, "ftm-slut" is most likely a tag used for porn videos featuring trans men or people with FTM experiences engaging in sexual activities and identifying themselves as sluts, expressing their desire for sex, kinks, and fetishes. The term "slut" here is used as a self-affirming, empowering, and sex-positive identity rather than a derogatory term. Remember that porn video tags are subjective and can vary between individuals and creators. This description is intended for an adult audience experienced with porn videos