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general::
Phrase(s): have one’s mind in the gutter [and] have got one’s mind in the gutter
Fig. tending to think of or say things that are obscene. • Tiffany has her mind in the gutter. That’s why she laughs at all that dirty stuff. • Why do you tell so many dirty jokes? Do you always have your mind in the gutter.
McGrawhill's American Idioms And Phrasal Verbs