Green’s Dictionary of Slang

(US) eccentric.

1965		T. Wolfe Kandy-Kolored Tangerine-Flake Streamline Baby (1966) 67: He is not a short-armed fatty hustling nutball fads.
1977		C. Larsen Midvale Chronicle 14: You listen to me, you little pervert! I'm not leaving my vast financial empire to a nutball kid!
1997		C. Hiaasen Lucky You 230: What if the nutball shooting sprees were an act and he was actually using the guns to signal the Negroes?
2004		Mad mag. Jan. 62: The nutball shirtless guy in Times Square.
2022		J. Hannaham Didn’t Nobody Give a Shit 213: [W]indmilling their arms [and] probably giving off nutball vibes.