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Retrofit is like .... ?

Here are the definitions of 'retrofit'
ret·ro·fit
1. 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.
2. To install or fit (a device or system, for example) for use in or on an existing structure, especially an older dwelling.
v.intr.
1. To fit into or onto equipment already in existence or service.
2. To substitute new or modernized parts or systems for older equipment: an industrial plant that was retrofitting to meet new safety regulations.
n.
1. Something that has been retrofitted or that has undergone retrofitting.
2. An instance of modernizing or expanding with new or modified parts, devices, systems, or equipment: a retrofit for the heating system.
adj.
Relating to or being a retrofit: a retrofit kit for the homeowner; an energy-saving retrofit program; a large retrofit market.