Usually used as an abbreviation to denote an
individual's identity as Transsexual, or
Transgender depending on personal preference.
Though the term is not specific with an individual's orientation. The term is typically used by Women (MTF), who have transitioned but have not opted for bottom surgery.
Commonly used in social
media bios and handles to inform viewers the content they will be indulging in taking preventing any surprises/confrontations from passersby. Not uncommon to see term used by NSFW influencers or entertainers to solicit community engagement from interested parties.
Boomer
Dad: "Hey, I matched with this 10/10 on tinder but her profile has TS. What does that
mean?"
Me: "Do not worry about it, gimme her
number so I can take her out on a date."