The fact that your guts still stays in the last timezone you travelled although you think you are way over jetlag.
1 "You may recovered from jetlag,but how come you still have to crap in the middle of afternoon ?"
"Oh ,that's just my gutlag."
2" Leave me alone! My guts's still on europe time."
"Ah, you are having that gutlag thing!"
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi