From Longman Dictionary of Contemporary Englisheye-openerˈeye-ˌopener noun [countable usually singular] SURPRISEDan experience from which you learn something surprising or new The whole trip has been a real eye-opener.
Examples from the Corpus
eye-opener• It had been my first alpine climb, and it had been an eye-opener.• A visit to a farm is an eye-opener to a city child.• I never put that much stock in images, and to have him do that-that was just an eye-opener.• It was an eye-opener, and it was puzzling.• It is not readily apparent that Edinburgh is a busy seaport but a visit to Leith Docks can be a fascinating eye-opener.• This can be a real eye-opener in many parts of the world.• Jimmy thought her a real eye-opener. 