1A festival — a traditional community or shrine event, often lively and celebratory.
夏になると各地で花火を伴う祭りが開かれる。
When summer comes, festivals with fireworks are held all over the country.
地元の祭りでは神輿を担いで街を練り歩く。
At the local festival, people carry a portable shrine through the streets.
子供の頃、祭りの夜店でりんご飴を買うのが楽しみだった。
As a child, I looked forward to buying candy apples at festival stalls.
来月、村の秋祭りが開催される予定だ。
The village's autumn festival is scheduled to be held next month.
2(colloquial) A situation where many internet users pile on to criticize or mock a particular post or person; an online flaming or mob pile-on.
その失言が拡散して、SNSで祭りになった。
That careless remark spread and turned into an online pile-on.
炎上した動画のコメント欄がちょっとした祭り状態だった。
The comment section of the video that went viral for backlash was in a bit of an online-mob state.
3(colloquial suffix) Attached to a noun to mean 'a frenzy of ~' or '~ galore' (e.g., a big sale event).
今日のセールはポイント還元祭りだった。
Today's sale was a points-back bonanza.
誕生日にケーキ祭りが開かれ、五種類も並んだ。
A cake extravaganza was held for the birthday, with as many as five kinds lined up.