Select the most appropriate meaning of the given idiom.

On the horizon

An event that is likely to happen soon

The most appropriate meaning of the idiom "on the horizon" is an event that is likely to happen soon. It is an informal expression that refers to something that is coming or approaching. The idiom is thought to have originated in the 17th century, and it is believed to be a reference to the fact that the horizon is the line where the sky meets the earth, and it is often used to represent the future.

The other options for the meaning of the idiom are incorrect. A plan for the distant future is not the same as an event that is likely to happen soon. The successful beginning of a business venture is not the same as an event that is likely to happen soon. An event that is likely to end soon is not the same as an event that is likely to happen soon.