kick in

Short definition from Wiktionary

Verb

1. 1
   To kick; to collapse or break by kicking: To kick or strike so as to cause the object struck to collapse or fall inwards.
2. 2
   To kick; to collapse or break by kicking: To kick or strike (a person); to beat up.
3. 3
   To begin, contribute or join in on: To start, connect, or take effect, especially in a sudden way; to begin functioning.
4. 4
   To begin, contribute or join in on: To join or begin.
5. 5
   To begin, contribute or join in on: To contribute, especially to a collection of money; to hand over.
6. 6
   To die; to give up on something.