Unseemly, insensitive, hearty laughter derived from mocking unfortunate things?
Still working on the definition, but I can share a quick sketch of the event that made me think of it. I was at a party at some loft, with a bunch of people I didn't know, all scattered about having their own conversations. I was sitting at the table and behind me, in some girl's room, I heard loud bursts of laughter. When a friend asked them what the hell they were laughing at, one of the girls said they were all looking at pictures of her ugly family. Then they laughed louder.