to provide a machine with a part, or a place with equipment, that it did not originally have when it was built

A state program to retrofit engines with pollution controls has succeeded in reducing pollution from trains. 州政府对引擎加装污染控制系统的计划成功地降低了火车的污染状况。

an occasion when a machine or place is retrofitted

Many hospitals are struggling to pay for the retrofits. 许多医院都缺乏升级改造的经济能力。