retrofit

Short definition from Wiktionary

Verb

1. 1
   To supply (a device, structure, etc.) with new components or parts that were not previously available or installed; to modernize.
2. 2
   To add or substitute (new components or parts) that were not previously available for or installed in a device, structure, etc.
3. 3
   Synonym of backport (“to retroactively supply a fix or feature to a previous version of a software product at the same time or after supplying it to the current version.”).
4. 4
   To give new characteristics or make alterations (to someone or something) to suit them to changed circumstances.
5. 5
   To supply a device, structure, etc., with new components or parts that were not previously available or installed.

Noun

1. 1
   An act of supplying a device, structure, etc., with new components or parts that were not previously available or installed; a retrofitting.
2. 2
   A change made to a device, structure, etc., by introducing components or parts that were not previously available or installed.