Word
Definitions
01person with secret knowledge
B2 · Upper Intermediate Countable noun
n. someone who knows how a company or group really works because they belong to it.
n. a person who has access to privileged information about an organization or institution due to their membership or employment within it.
“An insider leaked the news about the new phone before the company announced it.”
“Industry insiders suggest that the merger has been in development for months, despite official denials from the board of directors.”
Usage
Often used in the phrase 'industry insider' or 'insider trading'.
Teaching tip
While the word itself is neutral, it is frequently used in business and journalism to discuss leaks or specialized expertise.
Antonyms
02person inside a space
C2 · Proficiency Countable noun Formal
n. a person who is inside a specific room, building, or area.
n. a person located within the physical boundaries of an enclosed space.
“The police checked the building to make sure every insider was safe.”
“The security protocol required a full head count of every insider before the vault doors could be electronically sealed for the night.”
Teaching tip
This physical sense is rare in modern English; 'occupant' or 'person inside' is much more common.
Synonyms
Antonyms
Collocations
Common phrases and expressions where native English speakers use the word “insider” in context.
Adjective
01. corporate insider
“The journalist relied on a corporate insider to leak the documents regarding the company's tax evasion.”
adj + noun
02. political insider
“As a veteran political insider, she knew exactly which lobbyists to contact to get the bill passed.”
adj + noun
03. trusted insider
“The security breach was devastating because it was carried out by a trusted insider with high-level access.”
adj + noun
Noun
04. insider knowledge
“He used his insider knowledge of the merger to make a significant profit on the stock market.”
noun + noun
05. insider threat
“The IT department implemented new protocols to mitigate the risk of a malicious insider threat.”
noun + noun
06. insider trading
“The CEO was investigated for insider trading after selling his shares just before the stock price plummeted.”
noun + noun
Preposition
07. according to insiders
“According to insiders, the board of directors is planning to replace the current managing director by the end of the year.”
prep + noun
Real-World Examples
“BBC Sport's Chelsea reporter Nizaar Kinsella says insiders insist the chance will be gone and Fernandez will stay until next summer, if City do not make their move on Friday.” “Insiders at the biggest social media companies have previously told me how posts triggering a strong reaction are more likely to go viral.” “At a time when many opera companies are trying to make the art form more broadly inviting, Bayreuth’s determination to cater purely to insiders stands out.” Etymology
From inside + -er.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.
- Exam level
- CambridgeCambridgeCambridge English QualificationsThe exam suite from Cambridge University Press & Assessment, from A1 Movers up to C2 Proficiency. The benchmark names double as CEFR labels.C1 AdvancedIELTSIELTSInternational English Language Testing SystemThe 0–9 band test co-owned by the British Council, IDP, and Cambridge. Used for university entry, work, and migration.7.0–8.0TOEFL iBTTOEFL iBTTest of English as a Foreign Language, Internet-Based TestETS's academic English test, the standard route for US university admissions. Scored 0–120, with a 1–6 scale since 2026.1–6 scale: 5.0–5.595–113TOEICTOEICTest of English for International CommunicationETS's workplace English test, big in Japan and Korea. Listening & Reading scores 10–990 and tops out at C1.945–990
- Frequency
- Frequent
- Level
- C1 · AdvancedOxford
- Updated
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QR code
englishreference.com/q/insider
「カタカナ語」 data: JMdict (EDRDG), CC BY-SA 4.0