Real Dictionary

retrofit
verb: To retrofit a machine or a building means to put new parts or new equipment in it after it has been in use for some time, especially to improve its safety or make it work better.

retrofit in American English
a change in design, construction, or equipment, as of an aircraft or machine tool already in operation, in order to incorporate later improvements
to modify with a retrofit
adjective: being or characterized by a retrofit
intransitive verb: to fit into or onto existing equipment
noun: something that has been retrofitted
transitive verb: to modify equipment (in airplanes, automobiles, a factory, etc.) that is already in service using parts developed or made available after the time of original manufacture

retrofit in British English
verb: to equip (a vehicle, piece of equipment, etc) with new parts, safety devices, etc, after manufacture

retrofit in the Oil and Gas Industry
noun: A retrofit is the addition of new technology to older systems.