The word ground has several meanings:

The surface of the Earth
Soil, a mixture of sand and organic material present on the surface of the Earth
Ground (electricity), in electrical engineering, something that is connected to the Earth or at the voltage defined as zero (in the US, called ground; in the UK, called earth)
In philosophy, socially grounded arguments are those which take as their starting point social conditions.
In music, a ground bass is a bass part that continually repeats, while the melody and harmony over it change.
In plants, ground tissue is one of the three types of tissue systems in a plant.
In lace, the lace ground is the mesh surrounding the design.
To prohibit a child from leaving home, or to prohibit or prevent a pilot or airplane from flying.