noun
bottom part of a lidded box; box body without lid
Refers specifically to the container part of a box that has a separate lid, as opposed to the lid itself.
蓋を取って、身箱だけ使う。
Remove the lid and use just the box body.
この重箱は身箱と蓋がぴったり合う。
The body and lid of this tiered food box fit perfectly.
蓋 is the lid, while 身箱 is the bottom container part.
Compound of 身 (mi, 'body') and 箱 (hako, 'box'), with rendaku voicing of 箱 to ばこ.