cushion
n.β Β«CushionβClay that piles up in the corners from the sliding cars. Those who prefer to run on the outside of the track can use this to push off and zip down the straightaways.Β» ββLearning the Lernerville lingo” by Paul Kogut Valley News Dispatch (Tarentum, Pa.) May 14, 2004. (source: Double-Tongued Dictionary)