one who is hard to track or know whereabouts/one who lacks sense of responsibility
Definitions (粵典–words.hk)
名詞
成日唔知去咗邊嘅人（量詞：個／隻） somebody who often moves about without a trace; literally: tailless flying weight
你個冇尾飛砣，成日唔見咗人。
你个冇尾飞砣，成日唔见咗人。
nei5 go3 mou5 mei5 fei1 to4, seng4 jat6 m4 gin3 zo2 jan4. Why did you disappear? We don't know where you have been for the whole day.