weigant
Someone who makes things up as if they know what they are talking about, while very clearly sounding like a liar. Especially when attempting to sound cool or all knowing, and attempting to talk above people or act like a big shot.
When stating that he knew about how the government really works, David sounded like such a weigant. That person is such a weigant, they act like they know everything. Man I am sick of hearing that person's voice, they are such a weigant.