The Boston subway system. Represents the triumph of fuzzy logic, or something, because it does not actually stand for any single word. Cambridge Seven Associates thought it up in the early 1960s when the state hired them to design graphics for the then new MBTA. Their goal was to come up with something as recognizable as a cross that also evoked the idea of transit, transportation, tunnel, etc.
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).
Take the redline on the T from alewife to parkstreet, then change to the greenline at parkstreet until you get to Kenmore for Fenway Park.