Helen (ofTroy) suggested a discussion of gambling words, starting with horse racing.

Not that I know a good deal about it, as I go to the races infrequently, but I'd be a poor Marylander if I didn't know something about it and go to the track now and then. For openers:

Nag, screw: a worthless horse
Jock, rider, boy: jockey
Mudder: a horse that runs well in the rain or on a wet, sloppy track
Infield: the oval area inside the track
Tote board: the electronic parimutual board in the infield showing the details of the horses, the odds, and (after the race is over) the payoffs.
Bet across the board: a combination bet in multiples of 3 on the same horse for win, place and show.
Win: 1st place
Place: 2nd place
Show: 3rd place
Daily double: a combination bet on the winners of the (usually) 8th and 9th races
Exacta: a combination bet on what horses will win and place in any race
Trifecta: same as exacta, except on win, place and show in any given race
Morning line: the list of starters and the odds on each for all races at the track, as first published in the earliest editions of the newspaper or Racing Form