a stupid person► idiot/fool someone who does something very stupid or embarrassing: · You lost the tickets? How could you be such an idiot?· Anyone who tells you any different is either a fool or a liar.· Some idiot in a fast car is trying to overtake.· If you believe that, you're a bigger fool than I thought.· She was an idiot to drink so much on an empty stomach.make a fool of yourself (=do something that makes you seem very stupid): · It's increasingly common for the losers to go out kicking and screaming, and generally making fools of themselves.
► wally British informal someone who behaves in a stupid and annoying way: · Look at those wallies jumping around and pulling faces behind the TV reporter.· You look like a right wally in that hat.
► jerk especially American someone who is a little stupid and annoying, and who does not care if they upset or hurt other people: · Some jerk just drove right into the back of my car.· I liked the job, but the manager was a jerk.· Ow! You jerk, that hurt!total/real jerk: · She seems to always end up in a relationship with some total jerk.
► goof/goof ball American informal someone who is stupid and embarrassing: · He's such a goof. I don't know what she sees in him.· He always acts like a real goof after a couple of glasses of wine.· Oh Mike's okay, he's just a bit of a goof ball.
► dope American informal someone who is stupid and does not think about what they say or do: · I'm sorry I was such a dope last night.· Oh you dope, you bought the wrong one.
► dork especially American, informal someone who you think is stupid and strange because they behave strangely or wear strange clothes: · I look like a real dork in this uniform.· Millions of listeners heard him call his production assistant a 'dork' live on air.
British English informal someone who behaves in a silly way: 
Stop being such a wally!