protruding navel; outie
Refers to a navel that sticks out, as opposed to an innie. A common, everyday word.
The baby still has an outie, but it'll go in eventually.
He's a little self-conscious about his protruding navel.
Common mixed kanji-kana spelling; usually written in kana.
Kana-only spelling; the word is usually written in kana, so this is a natural written form.
Full kanji spelling using 臍 (へそ); rare in modern writing.
Compound of 出 (で, 'protruding') and へそ (navel). The kanji 臍 is used for へそ but is uncommon.