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Being difficult to deal with, short tempered, anal. Lacking a sense of humor, especially after someone has made a joke at your expense.

Typically used among medical students once they learn that the GUAIAC Test is the hospital test for blood in the feces. After the rectal exam, the gloved finger, now coated with feces, touches a special card. A few drops of chemical solution will change color if high levels of iron are present.
"Doctor, don't be so guaiatic."
by MSIII May 21, 2006
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