red flag (Noun) — A flag that serves as a warning signal. ex. "we didn't swim at the beach because the red flag was up"
red flag (Noun) — The emblem of socialist revolution.
red flag (Noun) — Something that irritates or demands immediate action. ex. "doing that is like waving a red flag in front of a bull"
red flag (Noun) — Emblem usually consisting of a rectangular piece of cloth of distinctive design.
red flag (Noun) — A listing printed in all issues of a newspaper or magazine (usually on the editorial page) that gives the name of the publication and the names of the editorial staff, etc..
red flag (Noun) — Plants with sword-shaped leaves and erect stalks bearing bright-coloured flowers composed of three petals and three drooping sepals.
red flag (Noun) — A rectangular piece of fabric used as a signalling device.
red flag (Noun) — Flagpole used to mark the position of the hole on a golf green.
red flag (Noun) — Stratified stone that splits into pieces suitable as paving stones.
red flag (Noun) — A conspicuously marked or shaped tail.
red flag (Noun) — (computer science) an option otherwise modifying the action of a command or program.
red flag (Verb) — Communicate or signal with a flag.
red flag (Verb) — Provide with a flag. ex. "Flag this file so that I can recognize it immediately"
red flag (Verb) — Droop, sink, or settle from or as if from pressure or loss of tautness.
red flag (Verb) — Decorate with flags. ex. "the building was flagged for the holiday"
red flag (Verb) — Become less intense.