1 And said, "Sir knight, these idle terms forbear,

idle > empty; foolish terms > words

2 And, sith it is uneath to find his haunt,

sith > since uneath > difficult

3 Tell me some marks by which he may appear,

marks > characteristics appear > come into view; hence: be recognized

4 If chance I him encounter paravant;

chance I him encounter > [I chance to encounter him] paravant > from before, in front; hence: before me, face to face

5 For pardie one shall other slay, or daunt:

pardie > truly; "by God" daunt > overcome, subdue