to stop doing something for a period of time or permanently:
When it rains, there is no alternative but to close up shop.
3if a group of people close up, they move closer together
close something ↔ up
if a wound closes up or if someone closes it up, the edges grow together again or are sewn together:
The scar is closing up nicely - it'll soon be time to take the stitches out.
5to become narrower or to shut:
The flowers close up at night.
Occasionally the channel widened then closed up tight again.
6to refuse to talk to someone about something:
The moment I said I was a police officer, everyone would close up like a clam.
close with somebody/something
1to agree a business deal with someone:
It was such a good offer that I closed with him on the spot.
2literaryto move towards someone in order to fight with them
WORD CHOICE: WORD CHOICE: close, shut, lock, turn/switch offIn many contexts, the verbs close and shutcan be used in exactly the same way• Please close OR shut the gate. • The windows were all closed OR shut. • She closed OR shut her eyes.• The store closes OR shuts at 7.!! Use closefor a road, border, or airport• All the crossing points on the border have been closed (NOT shut).!! Before a noun, use closed• a closed door (NOT shut door)!! You cannot say 'close someone somewhere'. Use shut or lockto say that someone is put in a room or building and cannot get out• They shut her (NOT closed her) in her bedroom. • He was locked (NOT closed) in a cell.Use switch off or turn offwith electrical things• Will you turn off (NOT close) the TV? • I switched off (NOT closed) all the lights.
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.