middleware

n. software connecting two different and separate applications (e.g., database to Web server)

'Middleware is computer software that sits 'in the middle' between application software (e.g. a word processing program) and the operating system (Unix, Windows, z/OS etc.) It is similar to operating system software in that it provides functions to multiple applications, and it is similar to application software in that it is not used for all applications, and that it eventually depends on operating system functions. Examples include database systems, telecommunications software, transaction monitors and messaging-and-queueing software.
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Software that mediates between an application program and a network. It manages the interaction between disparate applications across the heterogeneous computing platforms. The Object Request Broker (ORB), software that manages communication between objects, is an example of a middleware program.