- To provide (a jet, automobile, computer, or factory, for example) with parts, devices, or equipment not in existence or available at the time of original manufacture.
- To install or fit (a device or system, for example) for use in or on an existing structure, especially an older dwelling.
- To fit into or onto equipment already in existence or service.
- To substitute new or modernized parts or systems for older equipment: an industrial plant that was retrofitting to meet new safety regulations.
- Something that has been retrofitted or that has undergone retrofitting.
- An instance of modernizing or expanding with new or modified parts, devices, systems, or equipment: a retrofit for the heating system.
- Relating to or being a retrofit: a retrofit kit for the homeowner; an energy-saving retrofit program; a large retrofit market.