слабоу́мие

nounneuterinanimateuncountablevery rarely used (#18706)

1.
feeble-mindedness, imbecility, weak-mindedness, mental deficiency
У ребёнка диагности́ровали врождённое слабоу́мие.
The child was diagnosed with congenital mental deficiency.
Older clinical and general term; can sound offensive today.
2.
dementiamedicine
У ба́бушки ста́рческое слабоу́мие.
Grandma has senile dementia.
Especially in ста́рческое слабоумие 'senile dementia'.

Examples

Я не страда́ю слабоу́мием, я им наслажда́юсь.
I don't suffer from insanity; I enjoy it!
У старика начиналось старческое слабоумие.
The old man was beginning to develop senile dementia.