coast·er 
/ˈkoʊstɚ/ noun
plural coast·ers /ˈkoʊstɚ/ noun [count] 1 : a small, flat object on which a glass, cup, or dish is placed to protect the surface of a table
▪ Set the glass on a coaster. 2 chiefly US : roller coaster 1 3 : a ship that sails along a coast or that is used in trade between ports of the same country
▪ Set the glass on a coaster.
