kick in phrasal verb ( see also ↑ kick )
1 . informal to start or to begin to have an effect:
The storm is expected to kick in shortly after sunrise.
The painkillers kicked in and he became sleepy.
2 . kick in (something) to join with others in giving money or help SYN chip in :
Bill never wants to kick in.
We were each asked to kick in 50 cents toward the cost.
3 . kick sb’s head/face/teeth in to injure someone badly by kicking them:
He threatened to come round and kick my head in.
4 . kick a door in to kick a locked door so hard that it breaks open:
We had to get the police to kick the door in.