Douglas Harper's Etymology Dictionary
slang for "feeble-minded person," by 1914, American English, from feeble. Other words used in the same sense were feeble (n.), mid-14c.; feebling (1887).
Wiktionary
n. (context US slang English) Someone who is feeble-minded; an idiot.
Usage examples of "feeb".
Doctor Wilson was mad as could be, and said I was the worst feeb in the institution, along with Joe and Charley.
She had worked with grieving families during her time with the Feeb, and all of them had seen only questions in that terrible place of loss where no good answers exist.
The Feeb had taught her that all investigations begin at the crime scene, so she knew she would have to make the drive.
She had turned in her badge and FBI commission cardwhich agents called their credswhen she left the Feeb, but her wallet had been a gift from Marty.
Seems there was a complaint about you from one of the civilian instructors in the feeb unit.
Last time I was in the feeb mainframe, I left myself a couple of doors, you know, just in case we had problems like when the Russian got into the government systems?
Lots of feebs are scared of the dark, and Joe said he was going to have a fit right there.
Quent might not do handsprings, but the Feebs got off on stuff like that.
The young policeman had sounded out of breath and was sputtering with excitement, but Dutch finally interpreted the message: meet the feebs at the drugstore.
Local police often call in the Feebs to use their information systems and expertise, but the Buzz Cut had been around at almost every step in the dance.
Robbery-Homicide, how everyone was suddenly more relaxed, about the smiles and high fives, and even the grinning Feebs, and suddenly I knew there was more.
But the feebs had had some firearm training at this point, so he had their attention.
When she found this guy and turned him over to the feebs, she was hoping to get at least one clean kick at his testicles before they hauled him away.
Some civilian feebs ran the course at noon now and then, along with senior troops trying to stay in shape, but right at the moment he was the only one at the chin racks.
Those poor feebs were running around like a bunch of chickens with their heads cut off, going bug fuck crazy trying to keep the money systems from crashing.