Cask ale or Real Ale: a beer brewed from traditional ingredients (malted barley, hops water and yeast), matured by secondary fermentation in the container from which it is dispensed, and served without the use of extraneous carbon dioxide. (CAMRA Definition)
CAMRA: the Campaign for Real Ale, is an independent, voluntary, consumer organisation which campaigns for real ale, real pubs and consumer rights.
Firkin: Nine (9) Imperial Gallons or 72 Imperial pints (20 oz.). Common size of a Real Ale Cask. This was the size of the wooden beer casks of yore in England.
Pin: 1/2 a firkin. 4 1/2 Imperial Gallons. Another common size of a Real Ale Cask.
Polypin: Device for taking home cask ale. Usually available in 5, 10, and 20 Liter packages similar to boxed wine. Ask your local brewer for more info.
Beer Engine: Device to pump cask beer from the cellar to the bar.
Hand Pump: Device used to dispense the cask ale at the bar.
Gravity Pour: Way of dispensing cask ale directly from the cask via gravity, usually done at the bar in lieu of a Hanp pump and beer engine set-up.