1. 变卖(旧物)换进同类中较廉价的东西
    If someone trades down, they sell something such as their car or house and buy a less expensive one.

    e.g. They are selling their five-bedroom house and trading down to a two-bedroom cottage.
           他们要把 5 居室的房子卖掉，换一所较便宜的 2 居室小屋。