2 The knight his thrilling spear again essayed
thrilling > piercing essayed > attempted
3 In his brass-plated body to emboss,
emboss > encase; hence: bury
4 And three men's strength to the stroke he laid; 5 Wherewith the stiff beam quaked as afraid,
Wherewith > With which beam > shaft as > [as though]
6 And glancing from his scaly neck did glide
glancing > darting, shooting (esp. obliquely)
7 Close under his left wing, then broad displayed.
displayed > spread, spread out