roller coaster is a noun meaning "anything characterized by abrupt and extreme changes (especially up and down)". It carries 2 recorded senses.
anything characterized by abrupt and extreme changes (especially up and down)
“the economy has been on a roller coaster all year”
elevated railway in an amusement park (usually with sharp curves and steep inclines)
Definitions, synonyms and semantic relations for roller coaster come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.