red flag
noun/ˌred ˈflæɡ/
/ˌred ˈflæɡ/
- a flag used to warn people of danger
示警红旗 - You mustn’t swim when the red flag is flying.
红旗飘扬时不准游泳。
- You mustn’t swim when the red flag is flying.
- a red flag as a symbol of revolution or communism
（象征革命或共产主义的）红旗