Prancing

Prancing is the action of moving with energetic springy steps, often characterised by high kicks lively bounding, or a proud, strutting gait. The word is most frequently used to describe animals such as horses, but can also refer to spirited human movement. 

The term stems from the 14th century Middle English word "prauncen" and is often related to the Old Danish "pransk" (lively/spirited) or German "prangen" (to show off or be in a splendour)

In Chapter 50 of Far From The Madding Crowd, Boldwood use this in his dialogue to Bathsheba, "Hark! What's that prancing?" It merely means: "What's that galloping or stamping about outside?" 

Hardy often uses horse related verbs very precisely, and here prancing evokes the image of an animal stepping high and energetically, drawing attention by its movement and noise.