subdirector

/ˌsʌb.dəˈrɛk.tər/
noun
  1. A person who is below the main director in rank, often assisting or managing a specific part of an organization.
    • The subdirector of the museum organized the new exhibit.
    • The subdirector handled the daily operations while the director was away.
    • She was promoted from assistant to subdirector of the research lab.