cushion
n.— «Cushion—Clay 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.» —“Learning the Lernerville lingo” by Paul Kogut Valley News Dispatch (Tarentum, Pa.) May 14, 2004. (source: Double-Tongued Dictionary)
Further reading
What if, instead of being an inanimate object, a dictionary were alive? That’s the idea behind a lavishly illustrated new children’s book called The Dictionary Story (Bookshop|Amazon) by Oliver Jeffers and Sam Winston. This is part of a...