From Elsmar Cove Quality Assurance and Business Standards Wiki
Z
z Score - The observed value of the z statistic
z Statistic - A test statistic whose distribution under the null hypothesis has expected value zero and can be approximated well by the normal curve. Usually, z statistics are constructed by standardizing some other statistic.
z Test - A hypothesis test based on approximating the probability histogram of the z statistic under the null hypothesis by the normal curve.
Zero Acceptance Sampling - aka C=0
Zero Defects - The quality concept of zero tolerance for defects.