What is the meaning of Game_over?

A message signaling that the game has ended, usually because the player failed (for example by losing all of their lives) but sometimes following successful completion of the game.

The end of some ongoing situation due to either failure or success, typically failure.

An appearance of a game over message.

To receive a 'game over' message.

To deliver to someone a 'game over' message.

Source: wiktionary.org