When you hug a person, and the other person purposely holds on too long. In addition to "holding on" too long they are also deriving some pleasure from aforementioned contact. This pleasure could be from loneliness, or sexual deviancy. Similar to Frotteurism, with the other party being partially cooperative until the slow roasting begins.
Dude, i'm never going over your aunt's house again. She slow roasted me pretty bad and I think I heard her moan.
You should have warned me about John, I gave him a hug to be polite and wouldn't let go.... that was the worst slow roasting I've ever gotten.
Damn that girl is fine, I'm gonna slow roast her for sure.