A teacher who, with just a few words, makes you want to bite your own arm off just so you have something to throw at her. In a word, boring to hell and back, and a total pain to deal with.

A phrase to describe someone who is cognitively degenerating. Synonym of "going off the deep end". Can have varying degrees of severity.

Reference to the song "Hey You" by Pink Floyd. The line "and the worms ate into his brain" makes no sense in an otherwise linear and literal narration throughout the lyrics.