Largely from Candice Hern's website here, just a list of a few terms I used in my story.
Almack's : Assembly rooms in London, where balls were held every Wednesday during the Season. Patronesses of Almack's determined who could come in and who could not. Anyone in trade, even aristocrats associated with trade, were not admitted.
Bath: A city in the southwest of England, located 13 miles southeast of Bristol, Bath is known for its natural hot springs. Very fashionable in the Regency era (Jane Austen lived there for a time).
bluestocking: A woman with unfashionably intellectual and literary tastes.
Bow Street Runner: Established in the 18th century, the Runners worked under the magistrate of Bow Street in London and were the first London police force. The Runners were detectives who pursued felons and cases across the country.
Bristol: A city in the Southwest of England, built on the Avon River, Bristol was one of the country's largest ports. In the 18th century, Bristol's prosperity was built on slave ships and Thomas Clarkson, an abolitionist, went to Bristol to collect information on the slave trade to bring back to Parliament as evidence. In the 19th century, Bristol's status as the largest port in England was slowly being overtaken by Liverpool.
Courtesy Titles: If a duke, marquess or earl has a son, the son can use one of their father's lesser titles as their own until they inherit their father's title. The title isn't official and it doesn't give them a seat in the Lords, so it's called a courtesy title because the heir is a commoner until they inherit the big title. Only the younger sons of dukes and marquesses use "Lord" with their first names, no one else does. So the Duke of Jamaica isn't also Lord John, he's Lord Jamaica. But his younger son can be known as Lord Tom LastName. All daughters of dukes, marquesses and earls use Lady with their first names. The younger sons of earls and all children of viscounts and barons use "The Honorable" before their first name as a courtesy title. Confusing? Yeah. Don't worry. I only went up as far as viscounts.
Debrett's Peerage:An encyclopedia of the aristocracy, listing titles, estates, family histories. Still exists.
Duke of Slut: Popular in Regency-set romance, the Duke of Slut is a manwhore who has reputedly slept with every woman in the ton, yet miraculously does not have an STD. For some reason, there are hundreds of Dukes running around in the Regency, when in reality, there are usually less than 40 alive at any one time in Britain. The Sunflower solemnly swears not to use dukes at all in her stories, as she's rather tired of everyone being a duke.
Floating Harbor:Bristol Harbor, on the Avon, which was a major tidal river, meaning that the tides were crazy in difference, making it difficult for ships to get in and out of the city and putting wear and tear on ships. In 1804-09, lock gates were installed in the harbor, giving the section of harbor a constant water level and diverting the river into a cut beside it.
Gretna Green: The first village over the Scottish border, where marriage laws were much looser than in England. Minors could marry in Scotland without permission, so Gretna is the Vegas of its day with quickie weddings.
Hackney: Regency era taxi.
Post chaise: Regency era bus
The Season: Refers to the London social season, lasting from early spring until late June, while Parliament was in session. This is when the rich converged on London to attend balls, lectures, opera, ballet, the theatre and when young ladies made their social debuts.
Titles: The British aristocracy goes like this: Duke, Marquess, Earl, Viscount, Baron. They are all accorded seats in the House of Lords in Parliament. Baronets and knights are titled, but not considered peers (the aristocracy was collectively known as the peerage) and do not have seats in the Lords. Dukes are addressed as "Your Grace;" the others are "my lord" or "your lordship." See courtesy titles for what the heirs to various peers were called before they inherited.
TSTL:"Too stupid to live." As in, a heroine who is "feisty" or "unconventional," but does incredibly dumb things in the course of the story, to be unbelievable entirely.
ton: From French, bon ton, meaning the fashion or good manners. The upper classes were referred to as "the ton."