p.a.

(noun) an electronic amplification system used as a communication system in public areas. Synonyms: public address system, P.A. system, PA system, P.A., PA.

(noun) an informal term for a father; probably derived from baby talk. Synonyms: dad, dada, daddy, pa, papa, pappa, pop.

(noun) a short-lived radioactive metallic element formed from uranium and disintegrating into actinium and then into lead. Synonyms: protactinium, protoactinium, Pa, atomic number 91.

(noun) a unit of pressure equal to one newton per square meter. Synonyms: pascal, Pa.

(noun) a Mid-Atlantic state; one of the original 13 colonies. Synonyms: Pennsylvania, Keystone State, PA.

(adv) by the year; every year (usually with reference to a sum of money paid or received). Synonyms: per annum, per year, each year, annually. Examples: "He earned $100,000 per annum." "We issue six volumes per annum."