What does "simpleton" mean?

A simple-minded person lacking common sense.

What is a synonym for "simpleton"?

Common synonyms include: addle, ament, blockhead, born fool, buffoon, bumpkin.

/ˈsɪmpəltən/ noun, slang

noun, slang ·Moderate ·High school level

Noun

1
A simple-minded person lacking common sense. derogatory, informal
"The stranger had crossed a sacred line. He had mentioned the men's mothers. Nothing could get him out of a beating now, even the fact that he was obviously a simpleton. Albeit a simpleton with a good vocabulary."
2
a person lacking intelligence or common sense wordnet

"This poor simpleton has been robbed of four gold pieces. Take him, therefore, and throw him into prison."

From simple + -ton (as in a surname). Compare French simplet, Italian semplicione.