Leading or presiding officer of an organized group
The chair, also chairman, chairwoman, or chairperson, is the presiding officer of an organized group such as a board, committee, or deliberative assembly. The person holding the office, who is typically elected or appointed by members of the group or organisation, presides over meetings of the group, and is required to conduct the group's business in an orderly fashion. In some organizations, the chair is also known as president (or other title). In others, where a board appoints a president (or other title), the two terms are used for distinct positions.
https://en.wikipedia.org/wiki/Chair_(officer)