Bac

HP acquired Mercury at Feb 2007 and BAC now is in part of HP monitoring suite.
Baccalauréat
Bacalaureat
International Union of Bricklayers and Allied Craftworkers
Burlingame Aquatic Club - a swim team based at Burlingame High School.

Biochemistry
Bacterial artificial chromosome
Blood alcohol content or blood alcohol concentration

Short forms
Bac can also be used as a short form:
BAC is the shortened form of bronchioloalveolar carcinoma, a type of lung cancer often diagnosed in nonsmokers. (When pronounced it is spelled out B-A-C.)
Bac is often used as a shortened form for Baccalaureate.
Bac can also refer to the word "back" in IM or text messaging.