| an abnormal red blood cell having an elongated, crescentlike shape due to the presence of an abnormal hemoglobin. |

| sickle cell n. An abnormal, crescent-shaped red blood cell that results from a single change in the amino acid sequence of the cell's hemoglobin, which causes the cell to contort, especially under low-oxygen conditions. |
sickle cell sick·le cell (sĭk'əl)
n.
An abnormal, crescent-shaped red blood cell that results from a single change in the amino acid sequence of the cell's hemoglobin, which causes the cell to contort, especially under low-oxygen conditions. Also called drepanocyte, meniscocyte.