interjection, noun, noun or participle which takes 'suru', intransitive verb
A celebratory shout, traditionally made while raising both arms; also used as a noun or with する for doing the banzai cheer or gesture.
合格の知らせを聞いて、両手を上げて万歳した。
When I heard that I had passed, I raised both arms and shouted banzai.
優勝おめでとう、万歳！
Congratulations on the victory—hooray!
noun
cause for celebration; something to cheer about
Often used predicatively in expressions like それなら万歳だ, meaning that the outcome would be very welcome or worth celebrating.
予定より早く終われば万歳だ。
If it finishes earlier than planned, that will be something to cheer about.
noun, noun or participle which takes 'suru', intransitive verb
giving up; throwing one's hands up
A figurative casual use, based on the raised-arms gesture: to throw up one's hands because something is too difficult or hopeless.
この問題は難しすぎて、途中でバンザイした。
This problem was too difficult, so I gave up partway through.
noun
eternal life and prosperity
Literal or formulaic sense connected with wishing long life and prosperity; uncommon as an ordinary modern standalone noun.
古い祝辞では、万歳は長寿と繁栄を願う言葉として用いられる。
In old congratulatory speeches, 万歳 is used as a word wishing long life and prosperity.