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).
彼は100メートル走で最速のタイムを出した。
He recorded the fastest time in the 100-meter dash.
このルートが目的地までの最速の道です。
This route is the fastest way to the destination.