1.
If a group of people ~ on a person or place, they come nearer and nearer to them and gradually surround them.
Hitler himself committed suicide as Soviet forces were closing in on Berlin...
As Parretti walked across the tarmac, fraud officers closed in.
= move in
PHRASAL VERB: V P on n, V P
2.
When winter or darkness closes in, it arrives.
The dark nights and cold weather are closing in.
= descend
PHRASAL VERB: V P