Wiktionary
n. A cooked meal consisting of liver fillets with onions, especially sliced, and other seasoning.
Wikipedia
Liver and onions is a dish consisting of slices of liver (usually pork, beef or, in the United Kingdom, lamb) and onions; onion is favoured as an accompaniment to liver as the flavour of onion "cuts" the somewhat metallic flavour of liver, which can be off-putting to some eaters. The liver and the onions are usually fried or cooked together, but sometimes they may be fried separately and mixed together afterwards. The liver is often cut in fine slices, but it also may be diced.
Usage examples of "liver and onions".
He fried himself a big mess of deer liver and onions and heated up some more of the biscuits.
I closed my eyes and inhaled, buoyed up by the arty scent of liver and onions.
She was sauteeing liver and onions on the hot plate when she realized she ought to be doing more to help get Pierre out of the Lizards' jail.