Imbecile

Imbecile was an insult used typically to suggest stupidity.

The Fourth Doctor shouted "Harry Sullivan is an imbecile!", before passing out from the effects of a rockfall on Voga – caused by Harry. (TV: Revenge of the Cybermen) The Twelfth Doctor referred to Z-67, a gas created by Sullivan for use against Zygons, as "the imbecile's gas". (TV: 'The Zygon Inversion)