v.1. To enter something: I went in the garage to find a rake. I went in, and there was Grandma, sitting on the sofa. It's too cold on the porch—let's go in. I walked to the pond and went in for a swim.
2. To enter through something: If the front door is locked, go in the back door.
3. To go to a central or particular location: I called the office and told them I wouldn't be going in today. The car has to go in for service. I went in for surgery.
4. To belong to or be easily accommodated by some place: These forks go in the bottom drawer. I tried this key on the lock, but it wouldn't go in.
5. To be an added ingredient of something: What kinds of spices go in this sauce?
6. To be learned or understood: I explained the procedure to the new mechanic many times, but it didn't go in.
7. To take part in a cooperative venture: I went in with my friends to buy a present for our new neighbors. He'll go in with them on the plan. Who wants to go in on a pizza with me?