• 祭まつり — festival
• 祭まつる — to worship / to enshrine
• 文化祭ぶんかさい — culture festival
• 学園祭がくえんさい — school festival
• 大祭たいさい — grand festival
• 祭礼さいれい — ritual / religious ceremony
• 祭典さいてん — festival event

The kanji 祭 combines 示 (“altar”) and 肉 (rendered as 月 here) with 又 (“hand”), suggesting an offering at an altar. It originally depicted presenting meat to the gods; today it also refers broadly to festive events and celebrations.