burette, laboratory apparatus used in quantitative chemical analysis to measure the volume of a liquid or a gas. It consists of a graduated glass tube with a stopcock (turning plug, or spigot) at one end. On a liquid burette, the stopcock is at the bottom, and the precise volume of the liquid dispensed can be determined by reading the A burette is used to accurately measure the volume of liquid that has been allowed to pour out of it. 0lwR.