EXAMPLES FROM THE WEB FOR CRACKPOT
So that crackpot, Graham, had finally come up with something definite.
They dismissed him as a crackpot, too, if they heard about him at all.
Therefore, it wouldn't have happened—outside the crackpot fringe.
These had to be investigated—every lousy, crackpot one of them.
Projective telepathy had only been a crackpot's idea back then.
The Navy would not stretch regulations for a crackpot civilian.
Maybe the guy was a crackpot or phony, but it wouldn't hurt to hear his story.
The letter was dismissed as "crackpot," and no precautions were taken.
"This wasn't a crackpot idea," she said, eyeing him as if he were another log for the fire.
Dark eyes rigid, unfocused, behind them Jim's own image of a crackpot redhead who was Callista's friend.
"mentally unbalanced person," by 1900, probably from crack + pot (n.1) in a slang sense of "head." Cf. crack-brain "crazy fellow" (late 16c.). Earlier it was used in a slang sense "a small-time big-shot" (1883), and by medical doctors in reference to a "metallic chinking sometimes heard when percussion is made over a cavity which communicates with a bronchus."