noun, noun which may take the genitive case particle 'no'
record high; all-time high
Used for the highest level ever recorded in a particular context, such as temperature, stock prices, or sales.
This summer recorded the highest temperature in history.
The stock price hit a new all-time high.
過去最高 also means 'record high', but 史上最高 emphasizes 'in all of history', while 過去最高 can refer to a more limited past period.
Compound of 史上 (しじょう, 'in history') and 最高 (さいこう, 'highest').