retrofit

verb

1. (transitive)To supply (a device, structure, etc.) with new components or parts that were not previously available or installed; to modernize.

   “Trams dating from 2012 have been retro-fitted with lithium batteries, with the conversions starting in 2018.”

   “The project involves retrofitting Google’s Pixel smartphones to certain subway cars to collect sounds and other data and feed it into Google’s Cloud. […] When asked why the devices were retrofitted on older models instead of newer ones, Sarno said the MTA typically uses older car models when making modifications in case there are any unwanted effects.”

2. (transitive)To add or substitute (new components or parts) that were not previously available for or installed in a device, structure, etc.
3. (transitive)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.”).

   “The bug was so bad that we had to retrofit our patch to the last three releases, as well as the newest release.”

4. (figuratively, transitive)To give new characteristics or make alterations (to someone or something) to suit them to changed circumstances.
5. (intransitive)To supply a device, structure, etc., with new components or parts that were not previously available or installed.

noun

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