Someone who believes they've got the answer to every question even if the question hasn't been asked or if they really don't have the answer (... but of course they believe they do). This is not a shy individual, but rather someone whose ego is over flowing primarily through their mouth, but seems to have come from the other end of their digestive system.
Standing in the door of his single wide, Mr. know it all gave me his latest real estate tips.
Mr. know it all told the CIA there were weapons of mass destruction in Iraq. Unfortunately, they were listening.
Someone who is a busy body and goes around explaining everything to everyone even though they know nothing about anything.
A Mr. know it all with a mouth that says it all and a nose that's in it all.
Bullwinkle sees your mower inside your garage and tries to start it, but ends up breaking the pull rope. Bullwinkle spends the next half an hour telling you what's wrong with the mower and why you'd be better off buying a new one. Turns out the lawn mower needed some gas.