[header] How to define abs [title] Do cardio. [step] Although cardio doesn't necessarily define abs or tone them, it's an essential part to losing any excess weight or decreasing any pesky fat that might be hiding your defined abs. [substeps] Include at least 150 minutes of cardio each week. 
This is the minimum amount that most health professionals will recommended. However, if you are not seeing results or want to see results quicker, you may want to consider increasing your cardio to about 300 minutes per week.