"Act the wisenheimer" is a phrase that is used to describe someone who behaves in a know-it-all manner, often being snarky or condescending towards others. Some synonyms for this phrase include "smart aleck", "wise guy", "smarty pants", "wiseacre", "smart mouth", and "know-it-all". All of these terms convey a sense of arrogance and disregard for others, and can often be used interchangeably with "acting the wisenheimer". It's important to be mindful of how we communicate with others and avoid being too overconfident or dismissive of their opinions or ideas.