The act of opening and expanding the anal cavity of ones partner and then proceeding, with cave diving gear (ie: Carabiner, ropes, headlamps, etc), and entering the damp ridged caves of your consenting adult. Occasionally returning to the surface for air.
If you ask people who actually go caving, spelunking is the derogatory term for stupid or unprepared cave trips. Origin: "spelunk" is the sound a clumsy caver makes when he slips and falls in a cave and lands in water.
If you don't take a helmet, more than one source of light, and a few friends into the cave with you, then you're not caving. You're spelunking.
1. (v) To explore virgin caverns, and or orafices. Best practiced with a helmet and possibly a light. (Unless it's scary looking, then forgo the light, but be sure to use the helmet!)
Timmy, my next-door neighbor and play-time doctor is multi talented--an accoplished physician and an experienced spelunker.