1.
helmet; samurai helmet
A helmet, especially the ornate helmets worn by samurai warriors. Also refers to decorative replicas displayed during Boys' Day (端午の節句) and other cultural occasions.
Samurai helmets are characterized by elaborate crests (前立) and face guards. Miniature 兜 are displayed alongside 鎧 (armor) and 鯉のぼり (carp streamers) during 端午の節句 (Boys' Day, May 5th) to wish for boys' healthy growth.
The idiom 兜を脱ぐ (to take off one's helmet) means to surrender or admit defeat.