coast ‧ er /ˈkəʊstə $ ˈkoʊstər/ BrE AmE noun [countable]
1 . a small thin object on which you put a glass, or cup, to protect a table from heat or liquids
2 . a ship that sails from port to port along a coast, but does not go further out to sea
⇨ ↑ roller coaster