| Noun | 1. P.A. - an electronic amplification system used as a communication system in public areasP.A. system, PA system, public address system, PAamplifier - electronic equipment that increases strength of signals passing through itcommunication system - a system for communicatingloudspeaker, loudspeaker system, speaker system, speaker unit, speaker - electro-acoustic transducer that converts electrical signals into sounds loud enough to be heard at a distancetannoy - a loudspeaker | Adv. | 1. p.a. - by the year; every year (usually with reference to a sum of money paid or received); "he earned $100,000 per annum"; "we issue six volumes per annum"per annum, per year, annually, each year |