1) Add new parts to 2) Component 3) Constituent 4) Element 5) Make backwards-compatible 6) Modernize mechanically 7) Modify a mechanism 8) Substitute new parts for old 9) Supply with updated parts 10) To backport 11) To modernize 12) Upgrade an old system 
to replace existing items with updated items.
The process of modifying a building's structure.
To modify a device or machine after its been purchased, either to improveon a design element or to replace a malfunctioning component. ... (09 Oct 1997) ... 
to replace existing items with updated items.
[n] - a component or accessory added to something after it has been manufactured 2. [n] - the act of adding a component or accessory to something that did not have it when it was manufactured 3. [v] - provide with parts, devices, or equipment not available or in use at the time of the original manufacture 4. [v] - fit in or on an...
Addition of a pollution control device on an existing facility without making major changes to the generating plant. Also called backfit. 
noun 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`
The process of modifying a building's structure.
An editing term
substitute new or modernized parts for older ones