2. Another term for a speleologist.
3. Etymology: "A cave bug; one who explores caves as a hobby", 1942, formed from obsolete spelunk "cave, cavern" (c.1300), from Old French spelunque, from Latin spelunca, "a cave, cavern, grotto", from Greek spelynx (genitive spelyngos). An adjective, speluncar "of a cave" is recorded from 1855.
Urban spelunking is also commonly referred to as "infiltration", although some people consider infiltration to be more closely associated with the exploration of active or inhabited sites.
In the U.S.A., it may also be referred to as "draining" (when exploring drains) "urban exploration", and "urban caving."