What is the best possible exercise for lower abs?

This is going to sound strange, but I actually have found that just contracting my lower abs while I’m standing throughout the day has greatly firmed up my lower abdominals. Regular crunches mostly work your upper and middle abdominals, which is why it probably seems like you’re not getting results in your lower abdominals.

Running running and more running, I did this for some time and by running up hill u notice a dif In like a week

He actually said exercise, not into specifics for what he wants. So Bicycles are the best lower abdominal exercise, along with hanging leg raises, full crunches should work too (A reverse crunch and a regular crunch together)
Contracting your abs is a technique called ab vacuums, breath in sucking your stomach as far as you can for 30 seconds then exhale doing the same. Simply contracting your abs should work too.

For definition running should work along or other forms of cardio if you hate running. To get definition for any bodypart you need to lose bodyfat you do that by eating right (not dieting), exercise, getting a good night’s sleep, staying stressfree, and playing by the 80/20 rule. Do the right thing 80% of the time; exercise, eat the apple and carrot sticks instead of the donut, and have fun for the other 20% have a beer, kick back and relax, go over to burger king and get a whopper. Just don’t get out of hand with it.

Hope this helps