To "BUMP" someone is to be completely annoying with constantly sending (calls, text messages, pictures, notifications etc.) to someone's cell phone. Most of the time it's useless things that are not important and can just be told to that person..in person. Sometimes when you BUMP someone you can actually lock up their phone and then they have to restart it, causing them to be extremely pissed. Best advice - if someone reads your message and doesn't respond, they either have no response or its for a reason. Don't BUMP people, or else you you'll be dubbed as desperate.
John - Dude, this chick keeps bumpin' my phone, its so annoying.
Alex - She probably wants to get with you man haha