Noun
numpty (plural numpties)
(Britain, derogatory) An idiot, dolt or fool.
No different to the corporate world where you can have the best firewalls and IPS in the world but if some numpty admin responds to a phishing email with their uid and password you’re screwed. Source: Internet
That's not a sentence from the novel you numpty I said, that sounds more like the title of the book! Source: Internet