Definition - What does Ground (GND) mean?
Ground, in the context of electronics, is the reference point for all signals or a common path in an electrical circuit where all of the voltages can be measured from. This is also called the common drain since the voltage measurement along it is zero.
Ground could also refer to the earth ground, literally connecting electrical equipment to the ground to prevent user contact with high voltages.
Techopedia explains Ground (GND)
Ground or grounding originally began as a safety measure to prevent accidental electrocution. Take for example the case of a refrigerator with a metal body, if for some reason the body becomes electrically charged, there would be nowhere for the electricity to go since it has rubber feet, until somebody accidentally touches it and is shocked. To prevent this, a wire is used to connect the chassis to the ground so that any rogue electrical charge would dissipate to the ground, hence the name. This connection is typically done via a grounding rod; all the appliances in a house are ideally connected to a common circuit ground and then connected to the literal earth ground via the rod. This is also used for lighting protection systems where lightning is gathered via a lightning rod, to prevent it from hitting something else, and then dissipated on the earth ground.
Ground means something entirely different for electronic circuits. It is considered as the common reference point to measure voltage against any point of the circuit and is considered to have zero voltage. It is also the common connection that all electrical components must connect to in one way or another in order to complete the circuit.