erst > recently (310.1)

2 Forth riding from Malbecco's hostless house,

hostless > inhospitable

3 Far off espied a young man, who fled

fled > [was fleeing]

4 From a huge giant, that with hideous

hideous > odious; immense

5 And hateful outrage long him chased thus;

outrage > intemperance; passion chased > [had chased]

6 It was that Ollyphant, the brother dear 7 Of that Argante vile and vicious, 8 From whom the Squire of Dames was reft whilere;