1Best, supreme, or wonderful — describing something as unbeatably good; also a common exclamation of enthusiasm or praise (colloquially spelled 「サイコー」).
昨日のライブ、最高だったね！
Yesterday's concert was amazing, wasn't it!
このケーキ、味が最高だね。
This cake tastes fantastic.
天気もよくて、最高の一日だった。
The weather was great too — it was a wonderful day.
2Highest, maximum, or uppermost — indicating the greatest possible degree, amount, or rank (e.g. maximum temperature, the Supreme Court).
今日の最高気温は30度になる見込みです。
Today's high temperature is expected to reach 30°C.
会社は今年度の予算の最高額を決める必要がある。
The company needs to decide the maximum budget for this fiscal year.
この件については、最高裁判所が最終的な判断を下す。
The Supreme Court will make the final ruling on this matter.