同流合污的英文：
[Literal Meaning]
same/prevalent custom/merge/dirty
to wallow in the mire with somebody

[解释]
指跟坏人一起干坏事。

[Explanation]
to associate with an evil person and do the evil things

[例子]
如果你和那些坏人同流合污，最后只能是死路一条。

[Example]
If you associate with those bad people and do the evil things, you will perish eventually.

[英文等价词]
Birds of a feather flock together.

Being engaged in speculation and profiteering, he wallowed in the mire with them.
他和他们同流合污，投机倒把。