A Delegate connector defines the internal assembly of a component's external Ports and Interfaces, on a Component diagram. Using a Delegate connector wires the internal workings of the system to the outside world, by a delegation of the external interfaces' connections.
OMG UML Specification:
The OMG Unified Modeling Language specification, (v2.5.1, p.191) states:
A delegation Connector is a Connector that links a Port to a role within the owning EncapsulatedClassifier. It represents the forwarding of requests (Operation invocations and Signals). A request that arrives at a Port that has a delegation Connector to one or more Properties or Ports on Properties will be passed on to those targets for handling.
Delegation Connectors can be used to model the hierarchical decomposition of behavior, where services provided by an EncapsulatedClassifier may ultimately be realized by one that is nested multiple levels deep within it.