- to explore caves, especially as a hobby.
Origin of spelunk
back formation from spelunker, spelunking
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Word Origin and History for spelunk
"cave, cavern," c.1300, from Old French spelonque or directly from Latin spelunca "a cave, cavern, grotto," from Greek spelynx (genitive spelyngos). An adjective, speluncar "of a cave" is recorded from 1855.
Online Etymology Dictionary, © 2010 Douglas Harper