1. the quality or state of being incestuous; involvement in or characterized by sexual relations between family members
Usage: formal; typically used in legal, medical, or academic contexts
2. the quality of being excessively inbred or self-referential within a closed group or system
Usage: figurative; used to describe insular or nepotistic practices in organizations, industries, or communities

Examples

• The social worker documented evidence of incestuousness in the family case file.
• Critics argued that the incestuousness of the film industry limited opportunities for outsiders.
• The board's incestuousness—with members all from the same background—raised concerns about bias.
• Legal statutes address the criminal nature of incestuousness in various jurisdictions.
• The incestuousness of the academic circle meant that most positions went to internal candidates.