The Full Form of PBOR is‍ Personnel Below Officer Rank.

An enlisted rank (also known as an enlisted grade or enlisted rate) is in some armed services, any rank below that of a commissioned officer. The term can be inclusive of non-commissioned officers or warrant officers, except in United States military usage where warrant officers/chief warrant officers are a separate officer category ranking above enlisted grades and below commissioned officer grades. In most cases, enlisted service personnel perform jobs specific to their own occupational specialty, as opposed to the more generalized command responsibilities of commissioned officers. The term “enlistment” refers solely to a military commitment (whether officer or enlisted) whereas the terms “taken on strength” and “struck off strength” refer to a service member being carried on a given unit’s roll