Glass Nuggets
Glass Nuggets (Also called Vase Filler or Glass Globs) are thick "nuggets" of glass varying in size typically no larger than 3in(76.2mm)that are rounded on one side and flat on the other.
Uses
These are often used for eyes, rocks, bubbles and other round things in Leaded Glass as they can easily be wrapped with Foil or Lead Came. Though due to them being circular, clusters of them will have large gaps to fill with Solder.
If made from a known COE glass, they can be used in Fusing projects.
They can also be utilized in Mosaic projects though they are thicker than normal glass and will protrude more from the surface.
Making Your Own
If you have a Kiln you can use glass scraps and fire them to a Full Fuse then hold it until the glass pulls in and rounds out. Then your options for these are near limitless as you can mix and match colors as you desire for your projects.
You can find a tutorial for making these at home at How To Make Glass Nuggets.