Much of this business involves retrofitting existing planes.这项业务主要是改装更新现有的飞机。

Damaged houses have been repaired, roads repaved and buildings retrofitted.受损的房子已经修好, 公路重铺了, 大楼也翻新了。

A retrofit may involve putting in new door jambs.房子翻新可能得给门装新框。