What is the meaning of the word "wake-up call"?

Definitions:

  1. a telephone call that you request be made a specific time in order to wake you up at that time, usually in hotels copy to clipboard noun
    • The visitor wants a wakeup call at 7 a.m. copy to clipboard
  2. a warning to take action concerning something that was overlooked or neglected copy to clipboard noun
    • the bombing was a wakeup call to strengthen domestic security copy to clipboard