To kick or strike so as to cause the object struck to collapse or fall inwards.
Upon hearing residents in the burning house, the passerby kicked in the front door and yelled to those inside.
To start, connect, or take effect, especially in a sudden way.
I took my medication an hour ago, and it hasn't kicked in yet.
To contribute, especially to a collection of money.
For the year-end party, we're asking each employee to kick in twenty dollars.