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СТОЙТЬ <СТАТЬ, ВСТАТЬ> ГРУДЬЮ (за кого-что) elev
[VP; subj: human or collect]
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to defend, fight for s.o. or sth. courageously:
- X стоял грудью за Y-a X defended (protected) Y with everything X had;
- X bravely defended Y;
- X stood up bravely for Y;
- [in limited contexts] X took a firm stand for Y;
- X stood firm;
|| [in military contexts] X-ы стояли грудью (за Y) Xs defended Y with their lives;
- Xs fought courageously (for Y);
- [in limited contexts] Xs put their lives on the line.
     ♦ Пусть только кто-нибудь попробует задеть её детей-она станет за них грудью. Just let anyone try to harm her children - she'll protect them with everything she has.

Большой русско-английский фразеологический словарь. — М.: ACT-ПРЕСС КНИГА. . 2004.