1 To dreadful shapes he did himself transform, 2 Now like a giant, now like a fiend, 3 Then like a centaur, then like a storm
centaur > {Fabulous creature with the head, arms and trunk of a man and the lower parts of a horse}
4 Raging within the waves: thereby he weened
weened > thought, supposed
5 Her will to win to his wished end.
win > persuade
6 But when with fear, nor favour, nor with all
with fear > [neither with fear]
7 He else could do, he saw himself esteemed,
else > otherwise