noun
convertible collar
A collar style that can be worn open or closed; often seen on trench coats and casual shirts. The term is a wasei-eigo blend from French 'soutien' and English 'collar'.
from French soutien · from English collar
このコートはステンカラーが特徴です。
This coat features a convertible collar.
ステンカラーのシャツを着ると、カジュアルな印象になる。
Wearing a shirt with a convertible collar gives a casual impression.