(m; pl. "Bnei Mitzvah"); literally, "son of the Mitzvah;" more correctly, the status of having reached the level of being obligated in all the responsibilities and entitled to all the privileges of an adult male, in Jewish Society. In Judaism, this status is attained when a young man reaches the age of thirteen years.
This milestone is considered a bitter-sweet time, a time when the parents have the "nachas," the "pleasure of seeing the fruits of their labor," their son growing into adulthood, but which is also a large step closer to his leaving their home.
The son is generally called up to make a "beracha" on the Torah at the first opportunity after he reaches this status, and may read the Parshah and/or the Haftarah. The father is also given an "Aliyah" after his son's, at which he recites the additional blessing, "Blessed is He Who has relieved me of the punishment of this boy."
A "Seudah," a festive meal, is often celebrated in honor of this event, at which the son may say some words of Torah.

This definition is in context to Judaism. See more contextual defintions for "Bar Mitzvah".