LYSANDER:
Ay me! for aught that I could ever read,
for aught=from anything
Could ever hear by tale or history,
The course of true love never did run smooth;
But, either it was different in blood —
blood=social status

HERMIA:
O cross! too high to be enthrall'd to low.
O cross! - an exclamation
too high=too high in social status

LYSANDER:
Or else misgraffed in respect of years —
misgraffed=wrongly grafted

HERMIA:
O spite! too old to be engag'd to young.
to young=to someone young

LYSANDER:
Or else it stood upon the choice of friends —
it stood=love relied

HERMIA:
O hell! to choose love by another's eyes.

LYSANDER:
Or, if there were a sympathy in choice,
sympathy=compatibility/agreement
War, death, or sickness did lay siege to it,
Making it momentany as a sound,
momentany=momentary
Swift as a shadow, short as any dream,
Brief as the lightning in the collied night
collied=coal-black
That, in a spleen, unfolds both heaven and earth,
spleen=fit
unfolds=reveals
And ere a man hath power to say ‘Behold!’
ere=before
The jaws of darkness do devour it up;
So quick bright things come to confusion.
quick=quickly
confusion=destruction