1) Airhead 2) Ass 3) Blockhead 4) Bonehead 5) Boob 6) Booby 7) Changeling 8) Clod 9) Cretin 10) Dimwit 11) Dingbat 12) Dodo 13) Dolt 14) Doofus 15) Dope 16) Dullard 17) Dunce 18) Dunderhead 19) Fool 20) Fuckhead 21) Goose 22) Hammerhead 23) Idiot 24) Knucklehead 25) Loggerhead 26) Lunkhead 27) Mooncalf 1) Effortless weight 2) Fool 3) Foolish person 4) Human 5) Individual 6) Mortal 7) Ninny 8) Person 9) Simple 10) Somebody 11) Someone 12) Soul 
[stock character] In folklore, a simpleton is a person whose foolish actions are the subject of often-repeated stories. Simpletons are also known as noodles, fools, and gothamites. Folklore often holds, with no basis in fact, that certain towns or countries are thought to be home to large numbers of simpletons. The ancient Greeks told tales...
• (n.) A person of weak intellect; a silly person.
Sim'ple·ton noun [ Confer French simplet , Italian semplicione .] A person of weak intellect; a silly person. 
[n] - a person lacking intelligence or common sense
simple noun a person lacking intelligence or common sense