Definition & Meaning of "dim bulb"in English

What is the origin of the term "dim bulb" and how is it used?

"Dim bulb" is an English slang term that appeared in the mid-20th century to describe a stupid or slow-witted person. It draws on the metaphor of a light bulb that shines dimly, implying limited intelligence or mental clarity. The term is used in informal speech, often humorously or teasingly, though it can also express mild frustration. It is derogatory but relatively mild compared with harsher insults, and its offensiveness depends on tone and context.