noun
round back (book spine)
Bookbinding term for a spine with a curved profile, as opposed to a flat spine (角背). The reading まるぜ is a variant.
See also: 角背
この辞書は丸背で、開きやすい。
This dictionary has a round back and opens easily.
角背 refers to a flat spine, while 丸背 is a rounded spine.
Compound of 丸 (round) and 背 (back/spine).