Bubble and squeak (sometimes just called bubble) is a traditional English dish: the shallow-fried leftover vegetables from a roast dinner. The chief ingredients are potato and cabbage, but carrots, peas, brussels sprouts, and other vegetables can be added. It is traditionally served with cold meat from the Sunday joint, and pickles. The name is a description of the action and sound made during the cooking process.
A prepared frozen version is available.
A recipe is available at the Wikimedia Cookbook.
The name bubble and squeak is used in (at least) South East England - it is also Cockney rhyming slang for "Greek". The dish is also referred to as bubble and scrape in other parts (which?) of the country.
See also: British cuisine