Grounder is a second-generation Badnik created by Dr. Eggman. Appearing in Sonic the Hedgehog 2, the Grounder is a remodelled version of the Burrobot. It has a larger body and is actually faster than its predecessor. It does not burrow underground, however. Instead, it hides behind cover and burrows through walls to catch Sonic by surprise.
For information on the Adventures of Sonic the Hedgehog character, see Grounder (AoStH).