A man who thinks with his penis instead of his brain. In other words, his actions aren't rational and decisions are totally driven by getting laid.
He has been paying his girlfriend's cable bill so he has an excuse to go over there and spend time with her in hopes of getting laid.. What a dickbrain.
When you're typing the greatest comeback of all time, but you start daydreaming about how awesome it's going to be and end up just typing some nonsense.
Dude. That was goingto be the sickest burn ever until you dickbrained it.