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One who makes a hobby of exploring and studying the cave that is surrounded by the annular muscle (i.e., the ass)and able to contract or close a bodily opening. A poostabber. A male homosexual/anal invader.
My friend Paul is a sphincter spelunker, thus he is constantly washing feces off his weener.
by Carter Jordan September 27, 2004
The art of going deep into and exploring a persons sphincter. Derived from the word spelunking which is another name used for exploring caves.
John: "Dude did you hear Brad was hitting on my girlfriend last night?"
Kevin: "Ya I heard about that, what a tool!"
John: "Na man he is a Sphincter Spelunker."
by k3r0s1n3 July 31, 2009