3 That short revenge the man may overtake,
That > [So that] short > quick, speedy; immediate
4 Whereso he be, and soon upon him light."
Whereso > Wherever light > fall
5 "Certes," said she, "I wot not how he hight,
Certes > Assuredly wot > know hight > is named
6 But under him a grey steed did he wield,
wield > manage, control
7 Whose sides with dappled circles were dight;
dight > arranged; hence: marked