What is the medical term meaning erythrocyte with an irregular shape?

Sickle Cell Anemia is a genetic disease where the red blood cell (erythrocyte) takes on a sickle or crescent shape instead of the normal biconcave disk. Whereas the normal RBC is flexible and can easily travel through tight places in the joints, the sickle cell has no "give" and will bunch up in those same tight places causing inflammation, pain and heat.