n. Synonyms: douchebag, blowhard, blackguard.
An annoying person who has little common sense. A waste of space. An arrogant person who has no talent.
The word is used repeatedly in the novel "The Moon is a Harsh Mistress" by sci-fi master Robert A. Heinlein
A yammerhead is:
1. The obnoxious guy sitting in the next table over at the restaurant, calling the waitress every five minutes because his drink is too warm, he does not have enough sauce, and the steak is a tad undercooked.
2. An idiot who objects to agreeing a proposal by unanimous consent because he wants to hear "debate," which is "essential in a democracy."
3. There is at least one in every room. If you cannot find him/her, then you are it.