Mush has a few different meanings:

1. A soft, thick mixture, often made by cooking something until it becomes pasty. Oatmeal can turn into mush if you cook it too long. Overripe bananas become mushy when they get brown and squishy. When snow starts melting and mixing with dirt, it becomes gray, wet mush that's no good for snowballs or sledding. The word suggests something that's lost its form and become unpleasantly soft.
2. A command shouted to sled dogs, telling them to start running and pulling the sled. In Alaska and northern Canada, mushers drive dog sleds by calling out “Mush!” along with other commands to steer and stop.
3. Overly sentimental or emotional talk, writing, or behavior. If a movie gets too sappy, with characters crying and hugging every few minutes, someone might call it mushy. A greeting card full of flowery language about how wonderful someone is might be dismissed as mush. Some people enjoy mushy stories, while others prefer things more straightforward and less emotional.