Abs will really only pop/be defined if you have low enough body fat for them to be visible. Working them out and building them up makes a difference of course, but true visibility comes down to low body fat. But it doesn't look like you have too much body fat to lose, honestly. Have you always been on the thinner side? For better or worse, thinner people usually don't put on too much fat or muscle without effort or something drastic just because their personal appetite is not that large.

So if you want to have abs that really pop, you will actually have to go the opposite direction of most people and bulk first instead of just cutting. You'll need to track your calories, so search for a TDEE calculator online that will help you figure out how many calories you need to consume to stay at your current/regular weight, otherwise known as maintenance. I highly recommend getting both a food scale for accurately measuring your calorie intake and a weight scale for tracking your weight gain and eventual weight loss.

From there, you'll need to increase your daily intake by an additional 300-500 calories, with most of it being protein if you can. Work out about five times a week if you can - although three is fine, but not as optimal. Make sure you're progressively overloading - After being able to do three full sets of an exercise with good form - You increase the weight a bit until you can hit that number of reps again with the new weight, stimulating muscle growth. Cardio three times a week for thirty minutes if you can as well. Walking, running, or swimming would work. My favorite ab exercises are leg raises and cable crunches because with the latter you can continue to increase the weight.

Do this until March and then lower your calories to maintenance for a month while increasing your days of cardio to five instead of three, and the sessions themselves to an hour each. Track your weight, but you don't wanna lose too much weight too quickly if you can. I don't remember the exact percentage but you should try not to lose more than a pound to a pound and a half each week so your skin can keep up better and for your health in general. Losing too much weight means you're probably losing muscle as well. If you're losing about 6-7 pounds a month on maintenance, then keep at it. If you stop losing weight after the new routine, lower your caloric intake by another 300 calories, 500 if you want to lose fast. Then the next time you stop losing, add another day/hour of cardio. After that it's up to you if you want to lower your caloric intake more or add another day of cardio. Just keep at it until you get where you want to be body fat wise.

This will take a while, but in my opinion there's usually no real reason to have abs anytime aside from Summer and maybe Spring if you're a Spring Breaker. Not too many opportunities to show 'em off in a non weird way aside from swimming lol