The assumption of both above comments is that there can be multiple commonly-used definitions of a word. Annoyance is using one of the commonly-used definitions that doesn't fit into the 'most' above. He asserts that the other definitions are not only incorrect but insane, and I think this answers your question - a definition can be incorrect in the case that it is insane. Though I think calling a definition 'insane' is an odd use of the word.