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The rectal symptoms associated with consuming a donner kebab/curry the night before.
Eugh, shouldn't have eaten that second donner last night, i'm burning up with a case of Japanese Flag Syndrome.
by Phil24 June 21, 2006
The sickness where you spend most of your time sitting on the toilet, usually the day after eating spicy fast foods.
Joe called in sick to work, said he had an extra spicy indian last night and his ass now looks like the Japanese flag.

Ah the old Japanese Flag Syndrome then? Rough day ahead for Joe!
by defunkt October 01, 2011