mental retardation

Noun

 * 1)  A developmental disability in which the person has a very low intelligence quotient, usually below 70, plus difficulty in multiple areas of daily life. Evidence of this disability must have appeared before the person reached adulthood for diagnosis.

Usage notes
This term is no longer an accepted medical term in the United States. In September 2013, the Federal Register, under the agency of the United States Social Security Administration (SSA), changed its guidelines and replaced "mental retardation" with "intellectual disability", due to the negative connotations and offensive nature of the word retardation, meaning "delay" or "hindrance", and the common use of retard and retarded as pejoratives.