spelunking

From spelunk +‎ -ing. Back-formation from spelunker. Attested since 1946.^[1]

spelunking (usually uncountable, plural spelunkings)

1. The practice or hobby of exploring underground caverns.

   Synonym: caving

   • 2001, Nancy Hathaway, The Friendly Guide to Mythology, page 277:

     In the great myths, the adventures are external, even when they involve such metaphorical spelunkings as the voyage into the underworld.

spelunking

1. present participle and gerund of spelunk

•   caving on Wikipedia.Wikipedia