In the Boston metropolitan region, many commuters ride the MBTA commuter rail. These trains often have a single bathroom stall, in which a bowl resides over a tank filled with a fetid blue fluid that is presumably designed to mask the stench of it's content. One may often look down and see a mixture of blue liquid with turds, toilet paper wads and used tampons floating around. Should one be unfortunate enough to have to use this facility, the user must beware. Because the bowl is positioned at least 3 feet from the surface of this toxic soup, splash back is inevitable. Toilet water is bad enough, but having your ass splashed by the blue stuff is referred to as the "Blue Lick". May also be encountered in portapotty's.
Tom: Man I gotta take a shit so bad I'm gonna go in my pants.
Fred: You might want to just go in your pants...
Tom: Fuckit I'm using the bathroom.
Fred: Good luck.
Tom waddles back with a disgusted look on his face.
Fred: What's wrong?
Tom: I got the blue lick! And there was no toilet paper! It's soaking through my underwear!