When one performs meaningless tasks on their cell phone. This includes things like re-reading old text messages and unnecessarily scrolling through their contact list. One resorts to phone doodling when they want to make themselves look cool, popular, busy, or important while in the presence of others.
Person 1: "Hey man you've been playing with your phone for awile now, what's up with that?"
Person 2: "Oh, I'm just texting back this chick I met at the bar last night."
Person 1: "No your not, your phone doodling you pathetic looser!"