You might think a parking crater is a particularly large pothole in a parking lot. Or it could be a high-tech robotic device that puts you car in a box - a crate - and stores it neatly stacked among other cars.
But it's neither. According to Angie Schmitt of Streetsblog USA, who coined the term (so she would know), "a parking crater is a depression in the middle of an urban area formed by the absence of buildings" usually because there is a parking lot.
Because there are 3.5 parking spots for every car in the United States.