IPA: /səˈpriːməst/
KK: /səˈpriːməst/
The highest or most extreme level of something.
In her opinion, this was the supremest form of art.
Supremest is formed from "supreme" (from Latin "supremus", meaning highest or utmost) and the suffix "-est" (indicating the superlative degree). The word "supremest" means the highest or utmost degree of something.
Think of 'supreme' as meaning the highest, and remember that adding '-est' indicates the highest degree of that quality.