1. affecting everyone/everything within an organization or situation
changes/job cuts/wage increases have been implemented across the board
If something happens or is experienced 'across the board', it happens to - or is experienced by - everyone involved. For example, there might be increases in taxes 'across the board', meaning that everyone will be affected by the increases. This expression is generally heard in a professional context, and it could relate to changes, policies, rules or laws, or anything by which everyone or every department or group in a situation is affected.