APA Definition

abbreviation
American Pharmaceutical Association.
Webster's New World
American Psychiatric Association.
Webster's New World
American Psychological Association.
Webster's New World
Webster's New World Law
(business) Initialism of American Pale Ale.
Wiktionary
symbol

(metrology) Symbol for the attopascal, an SI unit of pressure and stress equal to 10−18 pascals.

Wiktionary