Wisenheimer is a term used to describe someone who is overly confident and assertive, often to the point of being obnoxious. Synonyms for this term include know-it-all, smart aleck, smarty-pants, show-off, and wise guy. Other similar terms include braggart, blowhard, and conceited. While these terms are often used interchangeably, they do have subtle differences. For example, a know-it-all may simply have a lot of knowledge, while a wise guy is more likely to use that knowledge in a manipulative or dishonest way. Regardless of which term is used, they all describe someone who is often irritating and unpleasant to be around.