Chapter 11:

apoplectic (adj.): Apoplexy is a condition of sudden paralysis; a stroke. To be apoplectic, in this case, is to behave as if on the verge of having a stroke.
arbor (n): an outdoor area shaded by trees or, in this case, scuppernong vines on a lattice.
bedecked (adj.): adorned; covered (with decorations)
calomel (n.): a laxative; often used as a cure for intestinal worms
camellia (n.): a shrub with glossy evergreen leaves and waxy, rose-like flowers.
camisole (n.) a woman's sleeveless undergarment, usually worn under a sheer blouse
commence (vb.): begin
decreed (vb): A decree is an official order. As her older brother, Jem decreed what he and Scout would do.
degradation (n.): a state of low honour or moral character
dog-trot hall (adj.): a covered passageway between two parts of a building
escapade (n.): reckless prank
essence (n.): fundamental nature; most important quality
infuriated (vb.): angered greatly
interdict (n.): prohibition; restraint
livid (adj.): pale; lead-colored. Livid can also mean red, as in the color someone's face gets when that person becomes angry.
oppressive (adj.): overbearing; hard to put up with
palliation (n.): to palliate is to lessen the pain, or, in this case, fear and anxiety, of something without actually making the fear and anxiety go away. Calpurnia is not a great source of palliation; that is, she doesn't make the children feel any less anxious or fearful.
passé (adj.): old-fashioned
philippic (n.): a bitter verbal attack
plate (n.): dentures; dental plate
propensities (n.): inclinations or tendencies
reconnaissance (n.): examination
rectitude (n.): uprightness of character
relic (n): something of historic interest that has survived from the past. In this case, Scout is referring to a gun that would have been used in the Civil War.
skulked (vb.): to move or slink about in a sinister manner. The children are skulking in the kitchen because they are fearful of Atticus's reaction when he returns home.
syringe (n.): a device with a rubber bulb on one end and a narrow tube on the other: used to inject or extract fluids from body cavities.
tirade (n.): a long angry speech
tranquil (adj.): calm
umbrage (n.): offense
undulate (vb.): to move in waves or in a wavy manner
viscous (adj.): sticky

Chapter 12:

alien (adj.): not natural; strange
appalling (adj.): shocking; horrifying
asafoetida (n.): a strong-smelling (like garlic) substance made from a parsley-like plant; often used in folk medicine to repel illness
austere (adj.): stern and severe
boded (vb.): continued
church (vb.): To church someone is to bring a person to church for a special service that revolves around that person's needs or deeds.
clad (vb.): dressed
contemptuously (adv.): To behave or speak contemptuously toward someone is to treat that person as if he or she is unworthy or beneath one's dignity.
contentious (adj.) always ready to argue
denunciation (n.): To denounce is to strongly disapprove of or condemn something. The denunciation of sin in the reverend's sermon indicates his strong disapproval of sin.
diligently (adv.): industriously; in a hard-working manner
dispelled (vb.): driven away
ecclesiastical impedimenta (adj. + n.) items used during a church service
frivolous (adj.): silly; not serious
garish (adj.) showy, very bright or gaudy
habiliments (n.): outfits; clothing
inconsistent (adj.): not in agreement; incompatible
indignantly (adv.): angrily
lilac talcum (adj. + n.): Lilacs are a very fragrant flower. Talcum, often called talcum powder, is a fine talc, or powder, used for the body or face. Lilac talcum is lilac-scented talcum powder.
rotogravure print (n.): Rotogravure is a process of printing pictures; often photographs of pictures. Since rotogravure prints often appeared in newspapers, it is possible that the print in the church had been taken from a newspaper.
snuff (n.): a preparation of powdered tobacco, usually sniffed through the nose
tapeworm (n.): a parasite that can live in a person's intestines.
voile (adj.): a thin, cotton-like fabric