Definition of educationally subnormal in English:

educationally subnormal

adjective

historical
  • (Frequently derogatory) having a low or below average level of education or intelligence; specifically (of a child) having learning difficulties and considered unable to be taught in ordinary schools; abbreviated ESN.

noun

historical
  • (With the) educationally subnormal people or children collectively.

Origin

Early 20th century; earliest use found in Public Health Report.