A unit of volume used in bartending. U.S. bartenders use a teaspoon equal to 1/8 fluid ounce or 1/12 jigger; this is equivalent to about 3.7 milliliters
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}