Also known as Rough or Farmhouse cider but it generally bears little resemblance to the cider you can buy in bars, particularly Scrumpy Jack, though sometimes you can find Weston's Old Rosie which is a scrumpy of sorts.
Generally it is brought straight off the farm in plastic gallon containers, for consumption off the premises, though through a quirk of British Licensing Laws it is possible to get a license that allows you to sell cider and tobacco only so it is possible to find dusty sheds where you can drink it on the farm.
Scrumpy production is centered around two areas the West Country (Somerset, Devon, Gloucestershire, Herefordshire etc) and East Anglia/Norfolk. In the latter place a clear (filtered) version is produced, though more normally scrumpy is cloudy and blood-stained urine yellow to snot green in colour, depending how well it's been fermented. Both varieties are strong in alcohol and as well as rotten meat it's not uncommon to see extra sugar (=more alcohol) or petrol added to the mix, amongst other things. Taste doesn't really come into it (though lack of it might).
I had the good/mis-fortune to grow up in a cider-producing area (Gloucestershire) so scrumpy played a large part in my teenage years. As I know only to well drinking too much can have severe consequences, to wit, green diarrhea and alcohol poisoning (I once ended up with a hangover that lasted a week). Scrumpy is probably best neatly avoided on reflection.