If you are jazzed, you are excited and full of energy about something — you cannot wait. It is informal American English: I'm really jazzed about the trip.

If you are jazzed如果你jazzed you你 are excited and full of energy很興奮、充滿活力 about something對某件事 you cannot wait迫不及待。 It它 is是 informal American English美式口語: "I'm really jazzed about the trip."「I'm really jazzed about the trip」（我對這趟旅行超興奮）

It grew out of jazz, the lively music, but people now use it with no music in mind.

It它 grew out of源自 jazz, the lively musicjazz這種活潑的音樂 but但 people now use it現在大家用它時 with no music in mind腦中不一定想到音樂

Though actually, older slang also used jazzed for being on drugs; that is not the usual meaning today, and it is not the one a learner needs.

Though actually不過其實 older slang比較老的俚語裡 also used jazzed for being on drugsjazzed也可以指嗑藥 that is not the usual meaning today但那不是現在常見的意思 and也不是 it is not the one a learner needs學習者需要的那個

You would not put it in a formal letter or a school essay. British speakers mostly know it from US films and songs, not from their own daily talk.

You你 would not put it不會用它 in a formal letter or a school essay在正式信件或學校作文裡。 British speakers英國人 mostly know it大多認識這個詞 from US films and songs從美國電影和歌曲裡 not from their own daily talk不是從自己的日常對話裡

There is a close cousin, jazzed up, which means made livelier or more decorated; that is a different use.

There is a close cousin有一個很接近的親戚, jazzed upjazzed up, which means意思是 made livelier or more decorated變得更活潑或更花俏; that is a different use那是不同的用法