1) single-celled organisms that live in crab's and fish's digestive systems
2) A prank that can be used to people who you know that have had sex, used as an std
"hey elle, guess what?"
Elle: "what?"
"andy has microsporidian, which means you have it too"
Elle: "what? really?"
by Lord Frog of the Night November 17, 2005
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