A nonsense word invented by a radio comedian of the 1940s, meaning a (usually technical) part of some machine or device that he didn't really understand or know the propername for.
Describing someone who gives a bad first impression but is actually a good person. Someone who doesn't appear to be competent, yet is extremely capable at what he/she does.
Dr. Bruce is a spaz, but he's one of the best doctors I know. You wouldn't know it by looking at him...good lenses, bad frames.