Gibbosity is a rare word in English that describes a rounded or swollen protrusion on a surface. If you're looking for synonyms for this word, then you might consider using the following options: bump, lump, protrusion, swelling, hump, bulge, convexity, or knurl. These words can be used interchangeably to describe the same thing, depending on the context and the specific meaning that you want to convey. Whether you're writing about anatomy, geography, or design, there are many ways to describe the gibbosity using a variety of synonyms that can add depth and nuance to your writing.