nincompoop
nounUK /ˈnɪŋkəmpuːp/
US /ˈnɪŋkəmpuːp/
A nincompoop is a silly person who does foolish things.
He forgot his own birthday, the silly nincompoop.
OTHER MEANINGS
2. A person who lacks good sense or judgment.
Only a nincompoop would leave the car unlocked in this neighborhood.
3. A naive or gullible person easily tricked by others.
The con artist took advantage of every nincompoop in town.
4. A clumsy or inept person who bungles simple tasks.
That nincompoop spilled coffee all over the paperwork again.