na-adjective, noun
perfectly round; perfect circle
Used as a noun or na-adjective for a shape that is completely round, such as a circle, disk, full moon, or round object. The variants 真ん円 and まん円 belong mainly to this literal sense.
満月が真ん丸に見えた。
The full moon looked perfectly round.
フリーハンドできれいな真ん丸を描くのは
It is hard to draw a neat perfect circle freehand.
na-adjective, noun
adorably round; cute
Only when written 真ん丸 / まん丸
Affectionate, casual use, especially in speech by women or children, for something cute because it is round, plump, or round-eyed. It is not a general replacement for 可愛い.
このハムスター、まん丸でかわいい!
This hamster is so adorably round!
まん丸なほっぺの赤ちゃんがにこっと笑った。
The baby with cute round cheeks gave a little smile.