'retrofit' definitions:

A component or accessory added to something after it has been manufactured

The act of adding a component or accessory to something that did not have it when it was manufactured; "the court ordered a retrofit on all automobiles"

Provide with parts, devices, or equipment not available or in use at the time of the original manufacture; "They car companies retrofitted all the old models with new carburetors"

Fit in or on an existing structure, such as an older house; "The mansion was retrofitted with modern plumbing"

Substitute new or modernized parts or equipment for older ones; "The laboratory retrofitted to meet the safety codes"