If something is protuberant, it juts or bulges out, like Santa Claus's famously protuberant belly.
You might find your small dog adorable, with her flat nose and protuberant eyes, while your brother prefers the family cat. Something that's protuberant can also be called a protuberance, and we can trace both words back to the Late Latin protuberare, "to swell or bulge," from the roots pro, "forward," and tuber, "lump or swelling."