Hobnail is a pattern of raised dots that form a bumpy texture, most often found on glassware.
While this pattern isn’t exclusively associated with milk glass, I do tend to think of that type of glassware when it comes to this pattern. The two images below should help you get a good idea of what this looks like. It’s pretty easy to spot!
If you do a basic Google search, you’ll see a whole bunch of gorgeous pieces with this pattern. My favorites are the kinds with the colored glass and an opalescent hobnail pattern. Beautiful!