What does "button up" mean?

To fasten with a button or buttons.

What is a synonym for "button up"?

Common synonyms include: adjust, bang, bar, barricade, batten, batten down.

verb, slang

verb, slang ·Moderate ·High school level

Verb

1
To fasten with a button or buttons. transitive
"Button up your shirt cuff. It has come undone."
2
refuse to talk or stop talking; fall silent wordnet
3
To fasten all the buttons on a coat, or similar item of clothing, to keep warm. intransitive
"Button up well. It's freezing outside today."
4
To conclude; to finalize; to put the finishing touches (on). ambitransitive
"It's time to button up the meeting."
5
Alternative form of button up one's lip. alt-of, alternative
"He needs to button up."

Show 1 more definition

6
To seal off (a military vehicle or facility). US, ergative, slang, transitive
"Once buttoned up, NORAD's operation center can survive for more than 30 days without aid from the outside world."

"Button up your shirt cuff. It has come undone."