| Noun | 1. | extracellular fluid - liquid containing proteins and electrolytes including the liquid in blood plasma and interstitial fluid; "the body normally has about 15 quarts of extracellular fluid" interstitial fluid - liquid found between the cells of the body that provides much of the liquid environment of the body blood plasma, plasma, plasm - the colorless watery fluid of the blood and lymph that contains no cells, but in which the blood cells (erythrocytes, leukocytes, and thrombocytes) are suspended |