3 quotes from the pages of Wikipedia:
Six pack may also refer to: A colloquial term for a well-defined rectus abdominis muscle of the human abdomen.
It is the combination of the linea alba and the linea transversae which form the abdominal “six-pack” sought after by many people.
While the “sixpack” is by far the most common configuration of the muscle bellies of the rectus, there exist rare anatomic variations which result in the appearance of eight (“eightpack”), ten, or—even rarer—asymmetrically arranged segments. All these variations are functionally equivalent.
Are “beer bellies” and “six-pack abs” functionally equivalent? Maybe, but the irony of the joke hangs heavier in some cases than in others.
Although well-defined abdominal muscles are also call “washboard abs,” I’m guessing there are far fewer men getting tattoos of washboards. “Six-pack” is the more popular metaphor.
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