"밍숭맹숭하다"는 비표준어입니다. "맨숭맨숭하다","맨송맨송하다", "맹숭맹숭하다"가 표준어입니다. Even though "밍숭맹숭하다" is used widely in daily life, it is not a standard word. "맨숭맨숭하다","맨송맨송하다", "맹숭맹숭하다" are standard word. 맹숭맹숭하다 : 하는 일이나 태도가 겸연쩍고 싱거운 모양. 심심하고 어색하다 ex) 그냥 맨숭맨숭하게 보내기에는 아까운 날씨다 It's too fine a day not to do anything. 친구들과의 모임이 점점 맨숭맨숭해지고 있다 Getting together with my friends is becoming boring 하는 일 없이 맹숭맹숭 세월을 보냈다. 맥주가 거품이 빠져서 맛이 맹숭맹숭해졌다

It's very similar to "It lacks the bite"

밍숭맹숭 can refer to the feeling of being bored or a taste of flat. for example, when you get to know a girl, and you're attracted to her so you ask her out with some fantasy about her; she might have as gorgeous body as her face, she might have as a great sense of humor as her smile looks like. but the date turns out to be so boring and not as interesting as you want to have the relationship further. then you can say '데이트 밍숭맹숭하게 끝났어.' or when coke's sparking taste has gone, and it tastes super bland and vapid. you can also say '콜라 맛이 밍숭맹숭해.' so 밍숭맹숭 basically means to get bored ot not to be able to find specialty out of something. but we usually use the term in normal seaking when we have expectation to certain food, situation, object or person, but it turns out to be not as special as i expected.