noun
mess kit; soldier's cooking utensils
Originally military field cooking gear; now also used in camping and outdoor contexts.
祖父は戦争中、飯盒でご飯を炊いたそうだ。
My grandfather says he cooked rice in a mess kit during the war.
キャンプで飯盒炊爨に挑戦した。
I tried cooking rice in a mess kit while camping.
飯盒炊爨 is a set phrase meaning 'cooking rice in a mess kit'; 炊爨 alone is a formal term for cooking rice.
Compound of 飯 (han, 'rice, meal') and 盒 (gō, 'box, container'). The kanji 盒 is relatively rare and specifically refers to a lidded container.