When you cum carefully onto the small of a girls back and the jizz pools in the cleft. Optionally you can then move her around to play with the lava flow.
"Dude, I totally gave Nikki some back lava last night."

"What, like the pastry?"

"No, not baklava - BACK... LAVA.

"Oh... Gross."

"Yeah, and then I made her slap it so it erupted like a volcano! Then I made her clean it up... Stupid bitch!"
by Travisssss January 24, 2012
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