ENGLISH
REFERENCE

insider

n.
US //ˌɪnˈsaɪdɝ// UK //ɪnsˈaɪdɐ// in·sid·er
  1. 1 finance/trading (n.)
    C1 Advanced Technical Law

    someone who works for a company and uses private information to buy or sell its stocks.

    a person, such as a director or executive, who has access to non-public, price-sensitive information about a corporation.

    Example

    The government is investigating him for illegal insider trading.

    Example

    Regulatory bodies monitor unusual market activity to detect whether an insider is profiting from non-public information regarding upcoming quarterly results.
Origin

From inside + -er.

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