/ Dictionary / Index B BAC: Meaning and Definition of Find definitions for: BAC Pronunciation: [key] blood-alcohol concentration: the percentage of alcohol in the bloodstream: under the laws of most states, a BAC of 0.10 is the legal definition of intoxication, although a few states use a slightly lower percentage, as 0.08. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. baby tooth Bacabal Related Content Daily Word Quiz: rustic Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language