The fuzzy logic that dominates your thought process on a Sunday, usually the result of a long Saturday night.
Rob: Yo Liam, why did you order chicken fried steak from the 5-point. Bad order man. What were you thinking?
Liam: I dunno. Sunday Brain I guess.
When the only person in a group with an iPhone gets peer pressured into looking something up on the internet, usually to settle a dispute or bet.
Drew: How was camping last weekend?
Neil: Aight, but I was the only one with an iPhone so there was loads of iPressure.