From Foyle’s Philavery: A Treasury of Unusual Words, some choice selections coming soon to a post near you:

captious: inclined to find fault or raise trivial objections

claque: 1. a group of people hired to applaud a performer in a theater etc. or a speaker at a meeting; 2. a circle of admirers and flatterers

contumacy: stubborn refusal to obey or comply; resistance to authority

crepuscular: 1. relating to twilight; dim; 2. denoting animals that are active or appear at morning or evening twilight

enantiodromia: a process by which a strong force produces its opposite, and the interaction between the two

facinorous: extremely wicked

feculent: 1. polluted; fetid, filthy; 2. containing sediment or faeces

flagitious: 1. deeply criminal; utterly wicked; 2. infamous; scandalous; shamefully disgraceful

lethologica: the inability to remember a word or call to mind the right word