Similar to "lol," used in text situations where you want to show that you laughed, not in a pleased or amused way, but in a bitter, cynical, depressed, or angry way.
Associated with dry, humorless laughter, or short harsh laughs like "HA!"
You: "lolb yeah, shes a whore"
You: "good news: john mccain lost. bad news: barack obama won."
Buddy: "lolb! we r so screwed no matter wut. the usa is broke man"