- To kick or strike so as to cause the object struck to collapse or fall inwards.
- Go kick in the door!
- (intransitive, idiomatic) To start or connect suddenly.
- You have to push the switch hard to get the heater to kick in.
- (intransitive, idiomatic) To contribute, especially to a collection of money.
- For the year-end party, we're asking each employee to kick in twenty dollars.
- This is a worthy charity, so everyone should kick in.