button–down

button–down /ˈbʌtn̩ˌdaʊn/ adjective
button–down
/ˈbʌtn̩ˌdaʊn/
adjective
Britannica Dictionary definition of BUTTON–DOWN
always used before a noun
1 
a  of a collar : having the ends fastened to the shirt with buttons
b  of a shirt : having a button-down collar
2 
[more button–down; most button–down] often disapproving or buttoned-down /ˈbʌtn̩dˌdaʊn/ : having a very traditional and formal way of dressing, behaving, etc.