coaster

/ˈkoʊstər/
noun
  1. A small flat object, often made of cork, wood, or plastic, placed under a glass or cup to protect a table surface.
    • Please use a coaster so you don't leave a ring on the table.
    • She bought a set of coasters with pictures of famous landmarks.
    • I put my coffee mug on a coaster to protect the wood.
  2. A person or thing that coasts, especially a vehicle or rider moving without power.
    • The sled is a fast coaster on the snowy hill.
    • He's a coaster in class—he never studies but still gets average grades.
    • The old bicycle was a good coaster once we reached the top of the hill.
Synonyms
What does "coaster" mean? | whatsthatwordmean | whatsthatwordmean