1) Backwardness 2) Extreme mental retardation 3) Idiocy 4) Imbecility 5) Intellectual deficiency 6) Lack of intellectual growth 7) Mental retardation 8) Retardation 9) Severe mental retardation 10) Slowness 11) Subnormality 1) Idiocy 
• (n.) Imbecility; total want of understanding.
A severe mental disturbance which renders a person incapable of comprehending the formal object of matrimonial consent or incapable of giving such consent. Ordinarily the term should properly be restricted to cases involving severe psychoses.
(ә-men´shә) former term for profound mental retardation.
Subnormal development of the mind, with particular reference to intellectual capacities; a type of
Absence of mind i.e. a mind that never developed or learning disability rather than a mind that was lost or dementia
A·men'ti·a noun [ Latin ] (Medicine) Imbecility; total want of understanding. 
Type: Term Pronunciation: ă-men′shē-ă Synonyms: mental retardation, dementia
amentia 1. Without normal mental abilities; such as, a congenital mental deficiency or mental retardation. 2. Mental disorder characterized by confusion, disorientation, and occasionally stupor. 3. Subnormal development of the mind, with particular reference to intellectual capacities; a type of severe mental retardation.
lack of intellectual development; imbecility; severe mental retardation.
[Difficult words] extreme mental retardation[Obscure words] extreme mental retardation