spelunker

As a letter s

is the letter s with a.

As a noun spelunker is

one who explores caves; one who spelunks.

As nouns the difference between claustrophobic and spelunker

is that claustrophobic is someone with claustrophobia while spelunker is one who explores caves; one who spelunks.

As an adjective claustrophobic

is (psychology) suffering from claustrophobia; being scared of being enclosed in a confined space.

As nouns the difference between spelunker and miner

is that spelunker is one who explores caves; one who spelunks while miner is a person who works in a mine.

As nouns the difference between spelunker and speleologist

is that spelunker is one who explores caves; one who spelunks while speleologist is a person who studies caves or the science of speleology.

As a noun spelunker

is one who explores caves; one who spelunks.

As a verb spelunked is

(spelunk).