One who explores caves chiefly as a hobby; a caver. (noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "spelunker" in a sentence
"The term "spelunker" was abandoned sometime in the late 1950s."
"Among serious cavers, "spelunker" has come to mean "person who goes underground without the proper equipment or training"."
"Never, ever, have I heard anyone speak of himself as a "spelunker," and the thought that someone might be about to spelunk is droll."