kidney

noun4

1. •
   one of a pair of organs near the lower back that take waste out of the blood as urine

   • An artificial kidney these days still means a refrigerator-sized dialysis machine. Such devices mimic the way real kidneys cleanse blood and eject impurities and surplus water as urine. — 2013
2. •
   This organ (of an animal) cooked as food.
3. •
   (figurative, old-fashioned) Constitution, temperament, nature, type, character, disposition. (usually used of people)

   • 30th June, 1788, Robert Burns, letter to Mr Robert Ainslie Your poets, spendthrifts, and other fools of that kidney, pretend, forsooth, to crack their jokes on prudence.
4. •
   (slang, no longer used) A waiter.