definition of
pa

[1] #1 pa n. [dad, dada, daddy, papa, pappa, pop] an informal term for a father; probably derived from baby talk. wn

[2] #2 pa n. [protactinium, protoactinium, Pa, atomic number 91] a short-lived radioactive metallic element formed from uranium and disintegrating into actinium and then into lead. wn

[3] #3 pa n. [pascal, Pa] a unit of pressure equal to one newton per square meter. wn

[4] #4 pa n. [Pennsylvania, Keystone State, PA] a Mid-Atlantic state; one of the original 13 colonies. wn

[5] #5 pa n. [public address system, P.A. system, PA system, P.A., PA] an electronic amplification system used as a communication system in public areas. wn