First-class and Upmost

First-class adjective - Of the very best kind.

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

Upmost adjective - Being at a point or level higher than all others.

First-class and upmost are semantically related in top topic. Sometimes you can use "First-class" instead an adjective "Upmost".