What does it mean when the American flag is flown upside down?

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6. What does an upside down flag represent?
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Tags

1. #never
2. #according
3. #symbol
4. #upside
5. #union
6. #should
7. #states
8. #instances
9. #except
10. #signal
11. #property
12. #meaning
13. #others
14. #pondered
15. #distress
16. #united
17. #extreme
18. #american
19. #danger
20. #displayed