First-class and Upper-crust

First-class adjective - Of the very best kind.

Upper-crust and first-class are semantically related. In some cases you can use "Upper-crust" instead an adjective phrase "First-class".

Upper-crust adjective - Of high birth, rank, or station.

First-class and upper-crust are semantically related. Sometimes you can use "First-class" instead an adjective phrase "Upper-crust".