Ejaculating an unfathomable amount of cum on a human males back, typically after engaging in homoerotic activities with a male (or trans male).
The word is stemmed from the phrase "light up my back."
"Dude, how was Thailand? Did you get any of their cheap sex massages?"
"Naw dude, I paid them extra to backlit me! It was awesome!"
The brand of political or social activism that involves doing nothing meaningful whatsoever except for completely useless gestures, "discussing the issues" with people who already share your point of view, and flooding Facebook with activism posts.
The whole point of which is simply to make sure everyone else in the world knows how tolerant and great you are and how shitty and tolerant they aren't, while actually not making any difference whatsoever.
That Tiffany girl who is always posting 10 times a day on Facebook about how society is controlled by anti-gay, anti-feminist, anti-immigrant, poverty-hating white guys gets drunk four nights a week on her parent's dime, and sleeps around while skipping half of the classes in her Development Studies major. She's never actually contributed to the betterment of society in any meaningful way. But pat yourself on the backtivism means she still thinks she's a better person than everyone else.
12 step recovery jargon referring to someone new who talks about how great life is, now that they'resober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.