to rob, bully, or verb someone. No matter what the case, frontin on somebody always has something to do with confronting them in some way. It comes from the word front, which means acting like something you aren't. So "fronting on" somebody is basically trying to make yourself look greater than you really are at the expense of that other person.
1. It's time to get on the front foot in the fight against HIV.
2. Front foot and strong mind essential to winning pitch battle.
Etymology: Cricket -- get on the front foot and attack the bowling. Take on the challenge.