noun, plural kid·neys.
- Anatomy. either of a pair of bean-shaped organs in the back part of the abdominal cavity that form and excrete urine, regulate fluid and electrolyte balance, and act as endocrine glands.
- Zoology. a corresponding organ in other vertebrate animals or an organ of like function in invertebrates.
- the meat of an animal’s kidney used as food.
- constitution or temperament: He was a quiet child, of a different kidney from his boisterous brothers.
- kind, sort, or class: He is only at ease with men of his own kidney.
- either of two bean-shaped organs at the back of the abdominal cavity in man, one on each side of the spinal column. They maintain water and electrolyte balance and filter waste products from the blood, which are excreted as urineRelated adjectives: nephritic, renal
- the corresponding organ in other animals
- the kidneys of certain animals used as food
- class, type, or disposition (esp in the phrases of the same or a different kidney)
early 14c., of unknown origin, originally kidenere, perhaps a compound of Old English cwið “womb” (see bowel) + ey “egg” (see egg (n.)) in reference to the shape of the organ. Figurative sense of “temperament” is from 1550s. Kidney bean is from 1540s, so called for its shape.
n. pl. kid•neys
- Either of a pair of organs in the dorsal region of the vertebrate abdominal cavity, functioning to maintain proper water and electrolyte balance, regulate acid-base concentration, and filter the blood of metabolic wastes, which are then excreted as urine.
- Either of a pair of organs that are located in the rear of the abdominal cavity in vertebrates. The kidneys regulate fluid balance in the body and filter out wastes from the blood in the form of urine. The functional unit of the kidney is the nephron. Wastes filtered from the blood by the nephrons drain into the ureters, muscular tubes that connect each kidney to the bladder. See also nephron.