Why is a horse "all snort and blow"?

You might have heard this saying - and it comes from a particular thing horses do. When a horse is over excited and eager, they often do something we call "blowing" - a rapid exhalation that creates a particular sound similar to a snort. "Blowing" is contagious behavior - once one horse in a group starts, the others will often join in, and then they get each other worked up.

In certain breeds, such as Saddlebreds, it's actually desirable - they want the horses excited and forward.