Sentence:  [T]he dog—a magnificent Newfoundland—that had come galloping down the field to meet us, began <WSD>curveting</WSD> round us, in gambols full of graceful beauty, and welcoming us with short joyful barks. 
Meaning of the word marked with <WSD> tags:  "Of a horse or, by extension, another animal: to leap about, to frolic.