Dressed to kill and First class

Dressed to kill adjective - Dressed in fancy or formal clothing.

First class and dressed to kill are semantically related. In some cases you can use "First class" instead an adjective phrase "Dressed to kill".

First class noun - Mail that includes letters and postcards and packages sealed against inspection.

Dressed to kill and first class are semantically related. Sometimes you can use "Dressed to kill" instead an adjective phrase "First class".