Deadly and First-class

Deadly adjective - Likely to cause or capable of causing death.

First-class and deadly are semantically related. In some cases you can use "First-class" instead an adjective "Deadly".

Nearby Word: dead

First-class adjective - Of the very best kind.

Deadly and first-class are semantically related. Sometimes you can use "Deadly" instead an adjective phrase "First-class".