There are four lines: Red (because it used to end at Harvard, whose color is crimson); Blue (it runs along the ocean); Green (it goes to the leafy suburbs of Brookline and Newton) and Orange (because it used to run above what was once known as Orange Street).
You'll sometimes hear references to the Purple Line (collectively all the commuter lines) and the Silver Line (a fancy-shmancy bus line that the T pretends is as good as a subway, running along the route of the old Orange Line elevated).
Girl friend, that party you threw was fabulous, the way you have your new apartment decorated is the deal and that new husband of yours is to die for! You are the T!
The T can also refer to getting the scoop or inside information about something.
RuPaul was preaching the T when she said, If you can't love yourself how the hell you gonna love anyone else.
I know he was checking me out. I wouldn't lie. I only tell the T.
Girl, you better tell me the T about what you heard from that bitch.
I'm not running my mouth, but let me drop the T on you.