Sentence:  And your great-uncle's, Edward the Black Prince, / Who on the French ground play'd a tragedy, / Making defeat on the full power of France, / Whiles his most mighty father on a hill / Stood smiling to behold his lion's whelp / <WSD>Forage</WSD> in blood of French nobility. 
Meaning of the word marked with <WSD> tags:  To rampage through, gathering and destroying as one goes.