1. Directions given that end up being incorrect or roundabout.
2. Placing one's buttocks on the car steering wheel, and using this as a method for navigating the car.
"Let me tell you the way" Bob said. Five minutes later, when Bob led them down a dead end street, he realised he'd taken his party on a bit of a bumsteer.
The trashy, lowerslung cousin of the hipster pant, favoured by female fashion victims, often those born without the ability to realistically determine their size. Although there is no agreed max-min amount of bumcrack to be shown, a visable 'brickies grin' is a key factor in determining whether the pant is a member of the bumster family.