The solid surface of the earth. The floor of a body of water, especially the sea. Soil; earth: level the ground for a lawn. An area of land designated for a particular purpose. Often used in the plural: a burial ground; parade grounds. The land surrounding or forming part of a house or another building. Often used in the plural: a guesthouse on the grounds of the mansion. An area or a position that is contested in or as if in battle: The soldiers held their ground against the enemy. Character witnesses helped the defendant stand her ground in the trial. Something that serves as a foundation or means of attachment for something else: a ground of white paint under the mural. A surrounding area; a background. The foundation for an argument, a belief, or an action; a basis. Often used in the plural. The underlying condition prompting an action; a cause. Often used in the plural: grounds for suspicion; a ground for divorce. See Synonyms at base1. An area of reference or discussion; a subject: The professor covered new ground in every lecture. The sediment at or from the bottom of a liquid: coffee grounds. Electricity A large conducting body, such as the earth or an electric circuit connected to the earth, used as an arbitrary zero of potential. Electricity A conducting object, such as a wire, that is connected to such a position of zero potential. To place on or cause to touch the ground. To provide a basis for (a theory, for example); justify. To supply with basic information; instruct in fundamentals. To prevent (an aircraft or a pilot) from flying. Informal To restrict (someone) especially to a certain place as a punishment. Electricity To connect (an electric circuit) to a ground. Nautical To run (a vessel) aground. Baseball To hit (a ball) onto the ground. Football To throw (a ball) to the ground in order to stop play and avoid being tackled behind the line of scrimmage. To touch or reach the ground. Baseball To hit a ground ball: grounded to the second baseman.