A Bar Mitzvah (literally, “son of law”, or, on A&E, “Son of Law & Order”) is a Jewish teenager who has been through a Jewish religious rite of passage, ceremonially and symbolically marking the age at which the child passes into young “adulthood”. In common usage, “get Bar-Mitzvah’d” and “at your Bar Mitzvah” are often heard. However, the words “Bar Mitzvah” actually refer to the person who is going through the rite of passage, as in “I became a Bar Mitzvah on May 10th, 2014” and “The Bar Mitzvah has arrived at his party!” Very often, to keep confusion to a minimum, Jews of Ashkenazi (Eastern European) descent will refer to the young man as a Bar Mitzvah Bocher (the “ch” is a clearing of the throat, not a “ch” sound like in “chihuahua”). The word “Bocher” is Yiddish for “young man”.

More information in the Bar Mitzvah article on Wikipedia.