Sentence:  But fleeter far the pinions of the Wind, / Which from Siberian caves the monarch freed, / And sent him forth, with squadrons of his kind, / And bade the Snow their ample backs <WSD>bestride</WSD>, / And to the battle ride. 
Meaning of the word marked with <WSD> tags:  To be astride something, to stand over or sit on with legs on either side, especially to sit on a horse.