1. A blood disorder in which there is excess fluid volume (of water) compared with the cell volume of the blood.
2. The excessive dilution of the blood, so that the proportion of serum to corpuscles is excessive.
3. A condition in which the blood volume is increased as a result of an increase in the water content of plasma, with or without a reduction in the concentration of protein; there is an excess of plasma in proportion to the cellular elements and a corresponding decrease in hematocrit (proportion of the blood that consists of packed red blood cells).
4. Excessive dilution of the blood, so that the proportion of serum to corpuscles is excessive; seen in splenomegaly (enlargement of the spleen) and other conditions.

A condition in which the blood volume is increased as a result of an increase in the water content of plasma, with or without a reduction in the concentration of protein; there is an excess of plasma in proportion to the cellular elements and a corresponding decrease in hematocrit (percentage of the volume of a blood sample occupied by cells).