"Lashing" is a "beating with a whip or strap or rope as a form of punishment"--this word and definition almost personifies the wind, which is supported by Charles Wallace's observation that "if I concentrate very hard I can understand the wind talking with the trees." But to Margaret (Meg), the wind is scary because it is a frenzied force lacking reason; worse, it seems to echo the direction of her own life and emotions.
In her attic bedroom Margaret Murry, wrapped in an old patchwork quilt, sat on the foot of her bed and watched the trees tossing in the frenzied lashing of the wind.
Behind the trees clouds scudded frantically across the sky.
During lunch she’d rough-housed a little to try to make herself feel better, and one of the girls said scornfully, “After all, Meg, we aren’t grammar-school kids anymore.
—You asked to have the attic bedroom, she told herself savagely.—Mother let you have it because you’re the oldest.
Wind blew in the crevices about the window frame, in spite of the protection the storm sash was supposed to offer.
"Fury" also has the "property of being wild or turbulent"--this would fit the nature of a high school teenager who's unhappy with the way she looks, upset that she is in danger of being left back in school, tearful because her father is missing, and willing to let her anger take on an older and heavier boy in a fight that results in her having a torn blouse and big bruise under one eye.
Meg would turn white with fury when people looked at him and clucked, shaking their heads sadly.
The furnace purred like a great, sleepy animal; the lights glowed with steady radiance; outside, alone in the dark, the wind still battered against the house, but the angry power that had frightened Meg while she was alone in the attic was subdued by the familiar comfort of the kitchen.
Meg looked up at her mother, half in loving admiration, half in sullen resentment.
“You don’t know the meaning of moderation, do you, my darling?”
The physical quality of Meg's voice at this moment is close to wailing. "Shrill" also means "being sharply insistent on being heard"--while Mrs. Murry hears Meg's protests, she is still going out in the storm to see what their dog is growling about. This makes Meg shrilly insist on going with her mom, because she doesn't want to end up losing another parent.
“I’ll go with you.” Meg’s voice was shrill.
“You peeked!” Charles cried indignantly. “We’re saving that for Mother’s birthday and you can’t have any!”
“Mrs Whatsit,” Charles Wallace demanded severely, “why did you take Mrs. Buncombe’s sheets?”
Meg looked sulkily down at the floor. “Nothing, Mr. Jenkins.”
"Ferocious" is not an adjective often used to describe braces, especially since braces are meant to straighten teeth to make them pretty instead of sharpening them to make them dangerous. The ferocity of the braces comes less from the barbed lines of wires and more from the way Meg is deliberately using them to reveal her anger at the principal's questioning of her father's occupation and whereabouts.
Meg bared her teeth to reveal the two ferocious lines of braces.
“Stop bellowing,” Mr. Jenkins said sharply.
“Do you enjoy being the most belligerent, uncooperative child in school?”
Try to be a little less antagonistic.
Maybe your work would improve if your general attitude were more tractable.”
Meg let out a stifled shriek.
"Peremptory" also means "offensively self-assured or exercising unwarranted power"--this could describe the nature of a five-year-old boy who both interrupts an adult while she's speaking and scolds her for stealing without consulting him first. But Charles Wallace's age actually makes him seem less offensive and his "uncanny way of knowing" gives him a powerful assurance that is scarily unusual.
But Charles Wallace held up his hand in a peremptory gesture.
I need fuel so I can sort things out and assimilate them properly.”
He clenched his fists. “But I love her. That’s the funny part of it. I love them all, and they don’t give a hoot about me.
“I guess so,” Meg said, but her happiness had fled and she was back in a morass of anger and resentment.
“My, but I wish there were no wind,” Mrs Whatsit said plaintively.
What grievous pain a little fault doth give thee!”