1. To cause something to crush, crumple, or collapse by striking it or exerting a lot of force on it. A noun or pronoun can be used between "smash" and "in." The demolition crew smashed in the house with a wrecking ball. Stop standing on the box like that, or you'll end up smashing it in!

2. To strike or collide with someone in a particular body part with great, violent force. A noun or pronoun can be used between "smash" and "in" to indicate who is being hit. She lobbed a brick over the wall, smashing a man on the other side in the face. The boxer smashed her opponent in the ribs with a devastating left hook.