insider

Definition

A person who has special knowledge about the inner workings of a group, organization, or institution.

Etymology

From inside + -er.

Example Sentences

• "Near-synonyms: initiate, old hand, habitué"
• "Heavy losses were sustained in Simms Petroleum, which took a greater toll from supposed "Wall Street insiders" than from the general public."
• "He is also an astute ANC insider who spent ten years on Robben Island alongside Nelson Mandela and the other “grandees” of the movement."