mental retardation

n. The state of lacking normal levels of intellectual capacity. There are several levels, usually labeled mild (IQ 52-69), moderate (IQ 36-51), severe (IQ 20-35), and profound (IQ 19 and below). Mild retardation is often the low end of the normal curve of intelligence; lower levels of retardation are due to brain abnormalities. Also called mental deficiency or developmental delay.