Drivers who position their cars intentionally to block other drivers who want to get by. Common on US Highways as a form of passive aggressive road rage, and illegal by statute in most states.
The prototypical Pass Prick rides right next to another car on a 4-lane highway so both lanes are blocked and nobody can pass. Closes gaps as fast as possible to form up another rolling roadblock.
Also a driver who accelerates quickly in front of everybody when lanes narrow to single lane, then drives slower than everybody. See also parade maker.
In rural areas, often a driver on two lane road who speeds up whenever their is room to pass, then slows to below speed limit when there is oncoming traffic