Lavatube 

Lavatube Noun/Verb
/lävət(y)o͞ob/
When a male has sexual relations with a woman for a long period of time (2 or more hours) the vagina becomes heated, thus creating a Lavatube, occasionally leaving male genitalia with blisters and sores.

Noun: "Bro I was going at it so hard her Lavatube burned my dick!"
Verb: "Make sure not to go at if for too long or she might Lavatube your dick!"

Lavatube by Apeirophobia June 30, 2016

Lavatubing 

Walking, hiking, crawling, or climbing through an ancient lava tube which is now free of lava flow, such as Ape Cave at Mount St. Helens. Probably involves the use of headlamps or flashlights.

Guy 1: "Hey man, what did you do this weekend?"
Guy 2: "Went lavatubing. It was awesome, I got cave bacteria all over my hands."

Lavatubing by anthroubc2010 October 1, 2010