Definition
A Tychonoff space X is p-realcompact iff every zero-set of βX that meets βX - X meets βX - υX.
βX represents the Stone-Cech compactification and υX represents the Hewitt-Nachbin realcompactification.
Reference
Mary Anne Swardson and Paul J. Szeptycki, When X^* is a P' space, Canad. Math. Bull. Vol. 39 (4), 1996 pp. 476-485.