kid ‧ ney /ˈkɪdni/ BrE AmE noun
[ Date: 1300-1400 ; Origin: Perhaps from Old English cwith 'abdomen, womb' + æg 'egg' ]
1 . [countable] one of the two organs in your lower back that separate waste products from your blood and make ↑ urine :
a kidney transplant
2 . [uncountable and countable] one or more of these organs from an animal, used as food:
steak and kidney pie