Definition of retrofits:
(v) :
(transitive) To supply (a device, structure, etc.) with new components or parts that were not previously available or installed; to modernize.
(v) :
(transitive) To add or substitute (new components or parts) that were not previously available for or installed in a device, structure, etc.
(v) :
(intransitive) To supply a device, structure, etc., with new components or parts that were not previously available or installed.
(n) :
An act of supplying a device, structure, etc., with new components or parts that were not previously available or installed; a retrofitting.
(n) :
A change made to a device, structure, etc., by introducing components or parts that were not previously available or installed.
(v) :
(transitive) (computing) 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.”).