Notes on Act IV, scene ii

sot: fool

cowish: cowardly

answer: retaliation (he ignores insults which would oblige him to retaliate)

wishes: desires that Edmund be her husband

prove effects: come true

brother: brother-in-law; she is unaware that Cornwall is dead

musters: collecting of troops

conduct his powers: lead his armies

change names: from that of wife to husband

distaff: stick used in spinning yarn, "woman's work"

stretch: raise your spirits (with a sexual innuendo as well)

Conceive: understand my intentions toward you

fool: husband

whistle: "It is a poor dog that is not worth the whistling."

contemns its origin: despises its parent

border'd: contained (he fears her infidelity)

disbranch: cut herself off from the family tree

text: on which your sermon is based

head-lugged: dragged with a chain around its neck, hence enraged

madded: driven mad

suffer: permit

discerning ... suffering: able to distinguish between injuries which affect your honor and thus should be avenged, and the patient endurance of ordinary troubles.

drum: preparing for war, calling men to battle

noiseless: no drum, thus unprepared

proper deformity: physical deformity, which mirrors the moral deformity within, is natural to a fiend/demon, but looks worse in a woman, in whom it is unnatural.

changed and self-cover'd: transformed as by witchcraft, disguising her true form

Be-monster: don't become in your looks the evil fiend you are inside 

Marry: by Mary

mew: she laughs at his manhood; mew can also mean to cage up

bred: raised

thrill'd: deeply moved

pluck'd him after: to death, following his servant

justicers: just gods to avenge crimes

nether: committed here below

this: the news of Cornwall's death, for it probably means Edmund's advancement to fill a powerful role

pluck: since my sister is now a widow, she may try to take Edmund from me, which would pull down all my dream-castles ("the building in my fancy"), leaving me here in this hateful marriage.

tart: sour (that is, things won't be so bad, if Cornwall's death means Edmund's advancement, and she can get her husband out of the way)