red flag means A warning sign in dating or friendships — a behavior that suggests incompatibility or trouble. It's mostly used in casual online conversation. It's casual and generally safe with friends and online. It's standard online vocabulary; nothing inherently concerning about hearing it.
red flag
A warning sign in dating or friendships — a behavior that suggests incompatibility or trouble.
red flæɡDocumented since 2010s2010sGen ZmainstreamCurrent7.8K viewsLast reviewed Jun 29, 2026＋ Add a definition
Seen in the wild
3 citations · last seen May 2026
Etymology timeline
Born ~2010 · 1 year of recorded useSeen in the wild
BlueskyMay 2026
Nationals new candidate for Auckland Central, anyone else spotting a red flag or two. #nzpol
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BlueskyMay 2026
The Lemkin Institute for Genocide Prevention has issued red flag warnings for genocide against trans people by the UK government. That's your very left-wing boys. Own it.
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BlueskyMay 2026
It's always a red flag for callous unseriousness when all prescribing is regarded as overprescribing, when they can't and don't want to define a use case for appropriate prescribing.
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Wikipedia: Flag of China
It is commonly called the "Five-star Red Flag" in China.
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Wikipedia: Flag of China
The Five-star Red Flag was adopted as the national flag of China upon the proclamation of the People's Republic of China on 1 October 1949.
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Definitions
Global
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#1·Apr 23, 2026GlobalCasual
A warning sign in dating or friendships — a behavior that suggests incompatibility or trouble. Compare with "green flag" (good sign) and "beige flag" (odd but neutral). "He doesn't tip waiters" has ended more relationships than any app algorithm.
"He doesn't tip waiters. Massive red flag."
Origin: Internet meme culture, 2010s–2020s.
For parents
red flag means A warning sign in dating or friendships — a behavior that suggests incompatibility or trouble. It's mostly used in casual online conversation. It's casual and generally safe with friends and online. It's standard online vocabulary; nothing inherently concerning about hearing it.
For ESL learners
"red flag" is slang. It means: A warning sign in dating or friendships — a behavior that suggests incompatibility or trouble. Register: casual. Use it in: casual conversation and online posts. Avoid in: formal writing and professional emails.
Cluster: romance
Heard in the wild
“Nationals new candidate for Auckland Central, anyone else spotting a red flag or two. #nzpol”
— Bluesky· May 2026“The Lemkin Institute for Genocide Prevention has issued red flag warnings for genocide against trans people by the UK government. That's your very left-wing boys. Own it.”
— Bluesky· May 2026“It's always a red flag for callous unseriousness when all prescribing is regarded as overprescribing, when they can't and don't want to define a use case for appropriate prescribing.”
— Bluesky· May 2026“It is commonly called the "Five-star Red Flag" in China.”
“The Five-star Red Flag was adopted as the national flag of China upon the proclamation of the People's Republic of China on 1 October 1949.”
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Comments (1)
Specifically flags a sign of incompatibility or trouble in dating or friendships, not just any minor annoyance — pair it mentally with 'green flag' (good sign) and 'beige flag' (odd but neutral) rather than treating every complaint as a red flag. — Slangora Editors
Show 4 more dictionary-style senses (imported)
Global
#2·May 2, 2026GlobalWork-OK
A cue, warning, or alert; a sign or signal that something is wrong.
Cluster: disapproval
Source: Wiktionary (CC BY-SA 4.0)
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Global
#3·May 2, 2026GlobalFormal
A flag formerly used by a railway guard to warn the driver not to start the train.
Source: Wiktionary (CC BY-SA 4.0)
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Global
#4·May 2, 2026GlobalFormal
Something that will enrage a particular person; a red rag.
Source: Wiktionary (CC BY-SA 4.0)
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Global
#5·May 2, 2026GlobalFormal
A flag that is red, especially associated with leftist revolutionary ideologies.
Source: Wiktionary (CC BY-SA 4.0)
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For specific readers
Why is this section here?
Slang is read by different audiences for very different reasons. The For parents view re-explains the term in plain, non-judgemental language so a caregiver can understand what their child means without needing the surrounding subculture. The For English learners view focuses on register (when it's safe to use), formal alternatives, and common mistakes — what a textbook won't teach you.
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🌐About Internet & Memes slang
Viral internet speak — memes, ratios, main-character moments, and the algospeak of every platform from Twitter to Reddit to TikTok comment sections.
See all Internet & Memes slang on Slangora.
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Other words near "red flag" (R)
Reddockred dogred drinkredd upred ensignred-eyered flag lawred flag warningred hatred-headed Eskimored horsered hot
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Semantically related
- green flag79%
A positive trait or behavior indicating someone is emotionally healthy, thoughtful, or a good match. "He asked about my day before telling me about his" is the archetypal green flag — small but diagnostic. Compare with red flag (dealbreaker) and beige flag (oddly specific).
- beige flag (dating)76%
Partner's oddly specific quirk that's not a dealbreaker but definitely weird — alphabetizing spices, only using plain WhatsApp, refusing to eat the ends of bread.