Word forms: plural red flags
1. countable noun
They waved red flags and shouted, 'Lenin, yes'.
Then the rain came and the red flag went up to signal a halt.
2. countable noun
If you refer
to something as a red flag
, you mean
that it acts as a danger signal.
The abnormal bleeding is your body's own red flag of danger.
COBUILD Advanced English Dictionary. Copyright © HarperCollins Publishers