noun, noun which may take the genitive case particle 'no'
completely visible; in plain sight; fully exposed
Describes a state where something is entirely visible, often with a nuance of being exposed or unable to be hidden. Commonly used for physical visibility, but also for secrets or private matters being laid bare.
カーテンを閉めないと、部屋の中が外から丸見えだ。
If you don't close the curtains, the inside of the room is completely visible from outside.
彼の嘘はみんなに丸見えだった。
His lie was plain for everyone to see.
丸見え is a noun/adjectival noun meaning 'completely visible', while 見える is a verb meaning 'to be visible' or 'to be able to see'.
丸出し also means 'fully exposed', but often implies something that should be hidden is blatantly showing (e.g., お腹丸出し 'belly fully exposed'). 丸見え focuses more on the state of being visible.
Compound of 丸 (まる, 'whole, complete') and 見え (みえ, the continuative form of 見える 'to be visible'). Literally 'completely visible'.