2 That blushing to her laughter gave more grace, 3 And laughter to her blushing, as did fall;
fall > happen
4 Now when they spied the knight to slack his pace,
to slack > [slackening]
5 Them to behold, and in his sparkling face 6 The secret signs of kindled lust appear,
appear > [appearing]
7 Their wanton merriments they did increase,
wanton > playful; lewd merriment > {Jest; piece of foolery}
8 And to him beckoned, to approach more near, 9 And showed him many sights, that courage cold could rear.
courage > sexual desire rear > excite, arouse