kick in
1. (Informal) To contribute (one's share): kicked in a few dollars for the office party.
2. (Informal) To become operative or take effect: "His pituitary kicked in, and his growth was suddenly vertical" Kenneth Browser.
3. (Slang) To die.
In order to achieve high levels of fault tolerance, you need to ensure that if any one of these fails, some system will instantly kick in and fill the void.
The above-mentioned is 2. i suppose
