Synonyms for P.A. (same or very similar meaning)
WordNet sense 1 (an electronic amplification system used as a communication system in public areas):
pa, public address system, P.A. system, PA systemWordNet sense 2 (by the year; every year (usually with reference to a sum of money paid or received)):
annually, per annum, each year, per yearFrom the ODE community, based on WordNetadd/edit