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1.
This is the unsightly excess fat that protrudes sideways at the meeting of the thigh and buttock. More commonly found on women due to their higher natural body fat.

Splidge flanks are usually caused by excess fat, though they can also be caused by ill-fitting trousers or jeans.
"Check out that fine ass! Too bad about the splidge flanks."
by Umbongo - England March 31, 2003