This porn video tag, "ts-dominatrix," is composed of two parts: "ts" and "dominatrix."
"Ts" stands for "transsexual" or "TS," which generally refers to a person who has undergone, is undergoing, or plans to undergo sex reassignment surgery. It can also be used as a catch-all term for trans women, including those who have not yet had surgery but identify as female.
"Dominatrix" refers to a woman who takes on the role of a dominant figure in BDSM (bondage/discipline, dominance/submission, sadism/masochism) scenes or relationships. This often involves the use of various sex toys, equipment, and techniques to control, tease, and stimulate their partners.
So, "ts-dominatrix" refers to a transsexual woman who takes on the role of a dominant figure in BDSM scenarios.