noun
protruding navel; outie
Refers to a navel that sticks out, as opposed to an innie. A common, everyday word.
赤ちゃんはまだ出べそだけど、そのうち引っ込むよ。
The baby still has an outie, but it'll go in eventually.
彼は自分の出べそをちょっと気にしている。
He's a little self-conscious about his protruding navel.
へそ is the general word for 'navel' or 'belly button', while 出べそ specifically means a protruding navel.
Compound of 出 (で, 'protruding') and へそ (navel). The kanji 臍 is used for へそ but is uncommon.