The surface of the Earth, as opposed to the sky or water or underground.

“Look, I found a ten dollar bill on the ground!”

Terrain.

Soil, earth.

“The fox escaped from the hounds by going to ground.”

To connect (an electrical conductor or device) to a ground.

To punish, especially a child or teenager, by forcing him/her to stay at home and/or give up certain privileges.

“Eric, you are grounded until further notice for lying to us about where you were last night!”

To forbid (an aircraft or pilot) to fly.

“Because of the bad weather, all flights were grounded.”