Sentence:  Brawny fighters, all cased in buff and iron, their hearts too sheathed in oak and triple brass, <WSD>caprioled</WSD> their huge war-horses, shook their death-doing spears; and went forth in the most determined manner, nothing doubting. 
Meaning of the word marked with <WSD> tags:  To cause (one's mounted horse) to perform a capriole.