or b.i.d.: Abbreviation for the Latin phrase bis in die, twice a day, a unit of frequency traditionally used by doctors in writing medical prescriptions
Russ Rowlett (Director), How Many? A Dictionary of Units of Measurement, Center for Mathematics and Science Education University of North Carolina, USA 2005. http://www.unc.edu/~rowlett/units/dictA.html, (Unit of Meas and Covr Factors - Amer) {608}