red flag

A red flag is either a literal warning of some danger, like the signal flag used by a sinking ship, or a figurative warning, like the red flag a candidate's angry outburst sends to the voters about his temperament.

Red flags have signaled dangerous situations for centuries, from seventeenth century military flags marking the start of a battle to a lifeguard station's red flag, warning beachgoers about dangerous water conditions. Even some spam filters refer to their junk email alerts as red flags. Figuratively, behavior is often a red flag: "He ate all my food and left the toilet seat up — it raised a red flag about choosing him as a roommate."

Primary Meanings of red flag

1.
n
a flag that serves as a warning signal
2.
n
the emblem of socialist revolution
Full Definitions of red flag
1

n a flag that serves as a warning signal

“we didn't swim at the beach because the red flag was up”
Type of:
alarm, alarum, alert, warning signal
an automatic signal (usually a sound) warning of danger
flag, signal flag
a rectangular piece of fabric used as a signalling device

n something that irritates or demands immediate action

“doing that is like waving a red flag in front of a bull”
Type of:
annoyance, annoying, irritation, vexation
the act of troubling or annoying someone
2

n the emblem of socialist revolution

Type of:
allegory, emblem
a visible symbol representing an abstract idea

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