-는 둥 마는 둥 하다

Partially doing, Barely doing, Without full effort

Explanation

This expression is used to indicate that the subject only partially or half-heartedly does some action and thus does not put his or her full effort into the task at hand. It is only used with verbs.

Details

This expression can be used in the form of -(으)ㄹ 둥 말 둥 하다 to express speculation about some future situation.

직접 가서 부탁해도 들어줄 둥 말 둥 한데 전화로 하면 되겠니?
They may not accept your request even if you go there in person, so do you really think you can do it over the phone?
밤을 새워 공부해도 시험에 합격할 둥 말 둥 한데 TV만 보고 있으니 한심하다.
There's no guarantee that you'll pass the test even if you study all night, but it's shameful to just watch TV.