Shell of medium size, but large for genus (up to 62.4 mm), light weight, fusiform, and broad (ratio of maximum width to length ~ .45); 7 inflated convex whorls, siphonal process short, recurved. Spiral sculpture of prominent cords on all whorls; axial rib sculpture prominent on all whorls with intersection of cords and ribs marked by raised pustules, squarish to somewhat spirally elongated. Suture distinct, slightly incised and usually marked by band of pustules. Apex subtends angle of ~ 40°, (apex of slenderest specimen examined subtends 33°). Teleoconch of 6 whorls, protoconch missing or damaged on all 15 specimens examined, remnants suggest large translucent embryonic whorls. Three spiral cords develop on first whorl and increase to 4-5 on penultimate whorl; most abapical cord often close to suture. 20-24 cords on body whorl extend up entire siphonal process. Concave space between cords with some fine lines. Prominent axial ribs develop on first whorl and extend suture to suture, increasing in number: 10-13 on next three whorls, 13-14 on penultimate whorl, 18-19 on body whorl. Aperture large, ovate, white, inner side of outer lip usually smooth, but occasionally with as many as 12 fine lirae, more numerous abapically. Outer lip convex, somewhat crenulate. Columella with elongate fold at entrance to canal. Shell color cream with broad caramel brown band adjacent to the adapical suture on last three whorls; the body whorl has a similar thinner band intersecting the lip at approximately the midpoint of the whorl. Operculum smaller than aperture (as is typical of genus), somewhat ovate, light brown.

There are two Granulifusus species that require comparison. The much smaller G. benjamini Hadorn & Fraussen, 2005 has a similar inflated profile (see, e.g., Hadorn & Fraussen, 2005: figs 71-72), but is only 21.2 mm in length and has fewer axial ribs. The quite variable G. kiranus Shuto, 1958 (Figs 7- 8) is about the same size as G. obesus and is found in the same general area. G. obesus has a much shorter siphonal process that is recurved, fewer whorls, and fewer axial ribs with spiral cords on entire shell. Most notably, G. obesus is much more inflated with a larger apical angle (40° vs 30°) and a larger width to length ratio (-.45 vs -.38).

Type locality: Indonesia, Timor Sea, depth 350 m.
Range and habitat: Timor Sea, from Indonesia southwards to northwest Australia