To serve jointly as a chairman or leader with another person; to co-lead a group, committee, or organization.
From 'co-' (together) + 'chair' (to preside), as a compound verb. Modern usage emerged in business and organizational contexts in the mid-20th century.
When organizations formally adopted the practice of co-chairing committees, they often found it reduced power struggles and improved decision-making—two equal leaders tend to compromise more than one all-powerful chair.
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