A person who tries to inject themselves into conversations where they think they have relevant knowledge and impress those around them with aforementioned knowledge. These people are inevitably proven to be morons by those around them with more than a quarter of a brain. When ignored they usually go away, calling them on their bullshit is another route to dismiss the PIF.
Matt: "That Andrew tried to lecture me again about the Philosophy of Plato."
Phil: "Yeah that guy is a pseudointellectual fuck. If old faithful spewed steaming nonsense instead of water it would be called Andrew."