不绝如缕[ bù jué rú lǚ ]

⒈ 象用一根细线连着，形容极其危急。现在也形容声音细微而连绵不断。例或者人已经转过山头望不见了，歌声还余音袅袅，不绝如缕。——《歌声》英almost extinct; very precarious like a thread going to break;