To be honest, instead of definition of abs I would rather work on things like having an athletic body, not necessarily ripped, but toned limbs, just the right amount of size of shoulders and arms etc and yes, work more on the facial muscles to get a stronger jawline. Yet, abs seem to be the "in thing", like whats the big deal about them, any skinny dude with low body fat can have them.
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To quote Elliot Hulse "abs on a skinny dude is like big tits on a fat chick--that shit don't count, lol"
If you have muscle and a six pack, it's a (relatively*) good indication of your physical fitness.
But your overall point is a good one -- abs are only one minor portion of the physique. Honestly, I think a ripped back and chest are more impressive. If you are exercising correctly, abs are just a nice little detail, not the main event.
*doesn't account for joint, ligament, and tendon health--most bodybuilders have poor health in those regards, between doing only partial ranges of motion and abusing steroids0