What is the term for a front along which a warm air mass overrides a retreating mass of cooler air?

The term for a front along which a warm air mass overrides a retreating mass of cooler air is called a "Warm Front".

Here are the steps that explain this process:

1. A warm front forms when a warm air mass pushes into a cooler air mass. This happens because warm air is less dense than cool air.

2. As the warm air mass advances, it rises above the cool air mass.

3. As the warm air rises, it cools and condenses, forming clouds. This can result in prolonged periods of light to moderate rain or snow, followed by warmer and clearer conditions.

4. The boundary line or front along which the two air masses meet becomes known as a warm front.

5. On a weather map, a warm front is usually drawn as a red line with semi-circles pointing in the direction of the warm air movement.