1
general::
Submit to an insult, rebuke, or other harsh treatment without resisting, as in He won't take that snub lying down. This idiom uses lying down in the sense of "passively." [Late 1800s] Also see TAKE IT, def. 2.
American Heritage Idioms
2
general::
Phrase(s): take something lying down
Fig. to endure something unpleasant without fighting back. • He insulted me publicly. You don’t expect me to take that lying down, do you? • I’m not the kind of person who’ll take something like that lying down.
McGrawhill's American Idioms And Phrasal Verbs