"Gravel" is already pretty well defined (drop bars, 650x47mm or 700x40mm), so I would go with adventure.
But I'm not sure what you'd do with this. I ran some 2.5" slicks on my Jones Plus for a bit, but they were total overkill on the road. Maybe bumpy gravel? We don't have many gravel roads around here, so it's hard to say.
But if you want this, the bikes are available. Jones and the Rivendell Clem Smith are two good examples. Salsa Fargo, etc.