Short for probability value.
p-value (plural p-values)
- (statistics) In statistical significance testing, the probability of obtaining a test statistic at least as extreme as the one that was actually observed, assuming that the null hypothesis is true. 
- ^ Goodman, SN (1999), “Toward Evidence-Based Medical Statistics. 1: The P Value Fallacy.”, in Annals of Internal Medicine, volume 130, pages 995–1004