- noun a non-proprietary system that is not under the control of one company
- noun a flexible type of organisation, which allows employees freedom to work in their own way
- noun a computer operating system that users are freely allowed to develop applications for
- noun a system that is constructed in such a way that different operating systems can work together
- A piping system for water or fuels in which the conduits that circulate the liquid are attached to an elevated tank or tower, with open vents to facilitate storage, access, and inspection.
- A system whose technical specifications are made public. In computers, for instance, this encourages third-party vendors to develop compatible products. This contrasts with a closed system, in which technical specifications are not made public.