noun which may take the genitive case particle 'no'
fastest; quickest
Used as a no-adjective to describe the fastest time, speed, route, method, etc. Often appears in compound nouns like 最速記録 (fastest record) or 最速ルート (fastest route).
He recorded the fastest time in the 100-meter dash.
He reached the goal in the fastest time.
This route is the fastest way to the destination.
She broke the fastest record for the marathon.
speed optimization; making something the fastest
Compound of 最 (most) and 速 (fast). The reading さいそく is the standard on'yomi combination.