ret ‧ ro ‧ fit /ˈretrəʊfɪt $ -troʊ-/ BrE AmE verb ( past tense and past participle retrofitted , present participle retrofitting ) [transitive]
to improve a machine, piece of equipment, building etc by putting new and better parts in it after it has been used for some time:
plans to retrofit oil boilers
—retrofit noun [countable]
—retrofitting noun [uncountable]