The definition is for "wanton" as a verb, but it is used as an adjective in the example sentence. "Wanton" usually has a sexually loose connotation, and although Shakespeare often includes sexual puns, that would not fit here, since Gloucester is focused on his miserably helpless state by comparing young boys' killing of flies to the gods' playing with human lives.
As flies to
wanton boys are we to the gods;
They kill us for their sport.
Here, Gloucester is recognizing that the gods have ordinances and order, and he is urging them to punish the humans who try to take too much for themselves. But he says this after almost everything has been taken away from him and right before he tries to take his own life--a life which had known excess lust (he'd fathered a bastard) and superfluous luxury (he was an earl).
Heavens, deal so still:
Let the superfluous and lust-dieted man,
That slaves your
ordinance, that will not see
Because he does not feel, feel your power quickly.
seize and take control without authority and possibly with force; take as one's right or possession
Goneril is deliberately misusing "usurp" here--as her husband, Albany ("my fool") has rights to her body, so he is not a usurper. Edmund is the one usurping Albany's rights (even though Goneril has freely given herself to him). By presenting herself as the usurped, Goneril is justifying her affair with Edmund, and any actions taken to secure the affair would be seen as righting a wrong.
In his use of the word "wither" Albany is both recognizing and insulting Goneril's power. As a withered branch (because she tore herself away from the tree of Lear), Goneril can be a deadly weapon. But as a withered woman, she would not be attractive to men.
She that herself will sliver and disbranch
From her material sap, perforce must
wither And come to deadly use.
The definition focuses on mental ability but Albany is talking about his physical ability. Because Goneril is a woman, ripping her apart would not be apt (appropriate), but if she weren't, Albany claims that he is apt (able) enough to do it. But Goneril's response doubts that Albany has any violence or strength in him.
Were it my fitness
To let these hands obey my blood,
apt enough to dislocate and tear
Thy flesh and bones. However thou art a fiend,
A woman's shape doth shield thee.
The King of France is supposedly returning home because something within his state requires his attention. But another reason he might have left is so that he wouldn't be seen as starting a war with England. Thus the definition of "import" as "bring in from abroad" could also fit here since Cordelia was an import whose decision to bring an army to save Lear can import great danger to France.
Something he left imperfect in the
state, which since his coming forth is thought
imports to the kingdom so much
fear and danger, that his personal return was
most required and necessary.
someone injured or killed or captured or missing in a military engagement
The definition of “casualty” does not fit the example sentence—although it hints at what will happen to Cordelia, “casualties” is referring to people or things that are casual (“not close or intimate” or “marked by blithe unconcern”), since Lear had given Cordelia away to a foreign king and sent her to live in a foreign land where she did not know anyone.
A sovereign shame so elbows him--his own unkindness,
That stripped her from his benediction, turned her
casualties, gave her dear rights
To his dog-hearted daughters--these things sting
His mind so venomously that burning shame
Detains him from Cordelia.
Cordelia wants to bring Lear peace of mind so that he doesn't end up killing himself. To remediate Lear's distress, Cordelia calls upon a doctor, the earth, and a French army. Compare this to what Edgar does to save Gloucester from suicidal despair.
All blest secrets,
All you unpublished virtues of the earth,
Spring with my tears. Be aidant and
remediate In the good man's distress. Seek, seek for him,
Lest his ungoverned rage dissolve the life
That wants the means to lead it.
As Edgar notices, Lear spits out reasonable truths along with mad rantings. Here, Lear is using images of armored warfare (plate, lance, pierce) to describe how the rich and poor receive different forms of justice: a rich person can sin and walk away unharmed, but if a poor person sins, he will be punished, often by a death sentence.
Plate sin with gold,
And the strong
lance of justice hurtless breaks:
Arm it in rags, a pygmy's straw does pierce it.