1 definition by Mopageboy

Top Definition
1) A depth of 6 feet
2) To think very hard
3) Your Anus. The bcakround behind this meaning comes from when two people were dune boarding and one fell off and loanded on my bum and said that his anus had stretched 6 feet open. now the word fathom is used to describe all bums not just a six foot wide one like his.
Whoa! that hole must be at least two fathoms deep

quiet you fool he is fathoming this question

Hahahahahaha he fell on his fathom while duneboarding!!!
by Mopageboy October 20, 2004

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