carabiner
noun [ C ] uk/ˌkær.əˈbiː.nər/ us/ˌker.əˈbiː.nɚ/
连接两件物体的扣（如登山扣）
an object used for attaching two things, for example by a climber for attaching a rope to a belt. It is oval or like a letter D in shape, with a part that opens and closes.
I unclipped my carabiner from the rope. 我从绳索上松开了登山扣。