Definition from Wiktionary, the free dictionary
- (informal, idiomatic) A startling or shocking revelation.
- A visit to the slaughterhouse was a real eye-opener to anyone who thought they understood where their food came from.
- (informal, euphemistic) An alcoholic beverage consumed first thing in the morning.
- As soon as I got on the plane I asked the flight attendant for an eye-opener, but all he had to offer was orange juice.