noun
imbecile; moron; feeble-minded person
Derogatory term for a person of low intelligence; often used as an insult. The variant 低脳者 explicitly links the meaning to 'brain'.
彼は怒って相手を低能者呼ばわりした。
He got angry and called the other person an imbecile.
そんな低能者扱いはやめてください。
Please stop treating me like a moron.
Compound of 低能 (low ability/intelligence) + 者 (person). The variant 低脳者 replaces 能 with 脳 (brain), emphasizing the perceived lack of brainpower.