The tendency, especially among males, to make educated (?) guesses about subjects and present them as fact. The syndrome manifests itself most frequently when the sufferer is asked a question by a member of the opposite sex.
Female: Do I need to put premium gas in my car?
Male: Absolutely. If you don't, you will short out your cam injector bearings.
Female: Uh, I think you are suffering from Male Answer Syndrome.