ultravacuum

/ˌʌltrəˈvækjuəm/
noun
  1. A space or container with extremely low pressure, much lower than a standard vacuum.
    • Creating an ultravacuum requires powerful pumps and careful sealing.
    • The ultravacuum chamber is used to simulate the emptiness of outer space.
    • Researchers study how atoms behave in an ultravacuum environment.