沃尔特在口袋里摸索，一个他以前抽烟时形成的习惯性动作。

Walt fumbled in his pocket, a reflex from his smoking days.

《柯林斯英汉双解大词典》

约翰模仿老板的习惯性动作。

John took off his boss's mannerisms.

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他也被用于描述习惯性动作或者状态。

It is also used to describe a habitual action and a condition.

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But another possibility is once you do something it's kind of hard to stop.

但也有可能是因为,婴儿很难使自己的惯性动作停下来

耶鲁公开课 - 心理学导论课程节选