"FTM-trans-guys" is an abbreviation for the term "Female-to-Male Transgender Guys". This term refers to individuals who were assigned female at birth but identify and express themselves as male. In a porn video context, it indicates content featuring trans men (previously identified as women) engaging in sexual activities with other trans or cisgender men. The tag is meant for adult audiences who have knowledge about the specific gender identities and are interested in this type of content.