Definitions

1. noun

a person who is jointly in charge of a committee or other group, especially one that has equal authority

“The cochairmen of the charity event worked together to plan the auction.”

2. noun

a person who shares the chairmanship of an organization with someone else

“The cochairman of the company’s board of directors oversaw the annual shareholder meeting.”

3. verb

to serve as cochairman of a committee or organization

“She was cochairing the city’s cultural festival along with her colleague.”