kidney

noun (plural kidneys)

• 1each of a pair of organs in the abdominal cavity of mammals, birds, and reptiles, that excrete urine.
• [mass noun] the kidney of a sheep, ox, or pig as food.

The kidneys' main function is to purify the blood by removing nitrogenous waste products and excreting them in the urine. They also control the fluid and ion levels in the body, by excreting any excesses. In the past the kidneys were thought to control disposition and temperament

• 2 [mass noun] nature or temperament:I hoped that he would not prove of similar kidney