An extremely offensive term for a transsexual man or woman, or any of the transgendered community.
On the same level as "nigger", and "cunt" for most people, though, like "dyke", some of the transgendered community are trying to reclaim the word, without much success.
Refers to trans people. If it’s a cisgender person using it, it’s a slur. Tranny (when used as a slur) usually refers to women. It’s been kind of reclaimed so some trans people refer to themselves as tranny.
TERF: He’s pretending to be a she. Fucking tranny.