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Jyutping se4 syu2 jat1 wo1
Pinyin shé shǔ yī wō

Definitions (粵典–words.hk)
  1. 語句
    古時​認為​蛇​同​老鼠​都​係​唔​好​嘅​動​物​,​所以​蛇同​老鼠​住​埋​同一​個​竇​,​就​用​咗​嚟​引伸​一班​壞人聚​埋​一齊​合作​做壞​事
    equivalent to "birds of a feather flock together" but only in a nefarious sense; in ancient times it was believed that snakes and mice were "bad" animals, and so occupied the same spaces; over time it was extended to refer to the phenomenon of bad people, such as criminals, generally hanging around and working with others of the same ilk; literally: snakes and rats in the same den
  2. 近義詞
    一丘之貉
Definitions (Wiktionary)
  1. phrase, idiomatic, of bad people
    to be working together; to be acting in collusion with one another

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Jyutping se4 syu2 jat1 wo1
Pinyin shé shǔ yì wō

Definitions (CC-CANTO)
  1. an idiom used to describe a group of people in the same syndicate and have the same intention (normally illicit or unpleasant intention) to carry out something harmful to others. Literally "snake and rat in the same nest"; act in collusion with each other