태엽이 풀리다

English rendering become slack Literal translation: “the spring unwinds”

Meaning 1

(속되게) 긴장 따위가 풀려 몸과 마음이 느슨해지다.

Colloquially, for tension to dissipate and the body and mind to become relaxed or slack.

Dictionary example 1

바쁜 때 지났다고 요새 태엽이 풀리는 모양이지?

Now the busy season is over, you seem to have let yourself go slack lately.

Dictionary example 2

한동안 휴가를 지내고 왔더니 태엽이 풀려 일이 손에 잡히지 않는다.

After spending a while on vacation, I have gone slack and cannot settle down to work.