A feeble-minded person is someone who has a mental disability or impairment. An 8-letter term for such a person is 'IMBECILE, ' which means having a very low level of intelligence. A 5-letter term is 'MORON, ' which is a milder form of mental retardation. A 6-letter term is 'DOTARD, ' which is an old person who is weak in mind or body. Lastly, a 7-letter term is 'HALFWIT, ' which is someone who is not very intelligent.