button-down

UK: /ˈbʌt^ədaʊn/ US: (but′n doun′)

WordReference Random House Learner's Dictionary of American English © 2025

ˈbut•ton-ˌdown,  adj. 

1. Clothing (of a collar) having holes at the ends with which it can be buttoned to the front of the garment.
2. Clothing (of a garment) having a button-down collar:
   a button-down shirt.
3. Also, ˈbut•toned ˈdown. too conventional or conservative:
   the button-down mentality of that company.

WordReference Random House Unabridged Dictionary of American English © 2025

but•ton-down  (but′n doun′), adj. 

1. Clothing (of a shirt collar) having buttonholes so it can be buttoned to the body of the shirt.
2. Clothing (of a shirt) having a button-down collar.
3. (esp. of attitudes, opinions, etc.) extremely conventional;
   unimaginative.

Also, but′toned-down′. 

• 1930–35, American.