feeblemindedness vs abnormality

feeblemindedness and abnormality both are nouns.

Word	Noun	Adjective	Verb	Adverb
feeblemindedness	Yes	No	No	No
abnormality	Yes	No	No	No

As nouns, abnormality is a hypernym of feeblemindedness; that is, abnormality is a word with a broader meaning than feeblemindedness:

feeblemindedness: severe mental deficiency
abnormality: retardation sufficient to fall outside the normal range of intelligence

Other hypernyms of feeblemindedness include mental defectiveness.

feeblemindedness (noun)	abnormality (noun)
severe mental deficiency	behavior that breaches the rule or etiquette or custom or morality
	marked strangeness as a consequence of being abnormal
	retardation sufficient to fall outside the normal range of intelligence
	an abnormal physical condition resulting from defective genes or developmental deficiencies