A ftm transsexual sibling. The word is a portmanteau of "trans" and "sister".
Airhead A: Is your sister still coming along to our girl's night out?
Airhead B: Sadly not; she's not a she anymore...
Airhead A: She's a TRANSTER now?
Airhead B: Like, yeah.
Airhead A: Oh, girlfriend, I'm so sorry for your loss!
A trans person who has a gangster origin.
"I just got mugged by a transter, damn." - Gangster Trans person.
"Hey, my transter! Wassup?" - Nickname.