internal organ, viscus

a main organ that is situated inside the body

• viscera, entrails, innards — internal organs collectively (especially those in the abdominal cavity)
• excretory organ, urinary organ — an organ that separates waste substances from the blood and discharges them
• liver — large and complicated reddish-brown glandular organ located in the upper right portion of the abdominal cavity; secretes bile and functions in metabolism of protein and carbohydrate and fat; synthesizes substances involved in the clotting of the blood; synthesizes vitamin A; detoxifies poisonous substances and breaks down worn-out erythrocytes
• heart, pump, ticker — the hollow muscular organ located behind the sternum and between the lungs; its rhythmic contractions pump blood through the body
• stomach, tummy, tum, breadbasket — an enlarged and muscular saclike organ of the alimentary canal; the principal organ of digestion
• respiratory organ — any organ involved in the process of respiration
• intestine, bowel, gut — the part of the alimentary canal between the stomach and the anus
• hindgut — the caudal part of the alimentary canal in vertebrate embryos

• organ — a fully differentiated structural and functional unit in an animal that is specialized for some particular function