ˈwake-up ˌcall noun [countable]

1. an experience or event that shocks you and makes you realize that you must do something to change a situation:
The success of extremist groups in the elections should be a wake-up call to all decent citizens.

2. a telephone call that someone makes to you, especially at a hotel, to wake you up in the morning Synonym : alarm call

[TahlilGaran] Dictionary of Contemporary English ▲

wake-up call
[American & Australian]
an event that warns someone that they need to deal with an urgent or dangerous problem.
The 1971 earthquake was a wake-up call to strengthen the city's bridges.
(often + to do something)
The World Trade Center bombing has served as a wake-up call to the FBI on terrorism.
(often + to)

[TahlilGaran] English Idioms Dictionary ▲