RBC: Short for red blood cells, the cells that carry oxygen and carbon dioxide through the blood. This rather remarkable feat is thanks to hemoglobin, the pigment that makes red cells (and blood) look red. The red blood cells are also known as red corpuscles or erythrocytes (literally, red hollow vessels).
RBC also stands for the red cell count, the number of red blood cells in a given volume of blood. The normal range varies slightly between laboratories but is generally between 4.2 - 5.9 million cells/cmm. This can also be referred to as the erythrocyte count and can be expressed in international units as 4.2 - 5.9 x 1012 cells per liter.