/ɪn'saɪdə(r); ɪn`saɪdɚ/ n person who, as a member of a group or an organization, is able to obtain information not available to others 内部的人; 知情人. insider `dealing (also in,sider `trading) buying or selling with the help of information known only by those connected with the business 内幕交易.

n[C]
someone who has a special knowledge of a particular organization because they are part of it
≠ outsider
　an insider's view of the way that a Japanese company works