—v.t. 1. 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.
2. to install, fit, or adapt (a device or system) for use with something older: to retrofit solar heating to a poorly insulated house.
—v.i. 1. (of new or modified parts, equipment, etc.) to fit into or onto existing equipment.
2. to replace existing parts, equipment, etc., with updated parts or systems.
—n. 1. something that has been retrofitted.
2. an instance of updating, enlarging, etc., with new or modified equipment: A retrofit could save thousands of dollars.
—adj. being or characterized by a retrofit: retrofit units.