As defined by Wikipedia: A professional association (also called a professional body, professional organization, or professional society) is usually a nonprofit organization seeking to further a particular profession, the interests of individuals engaged in that profession and the public interest.
As defined by Dictionary.com: a body of persons engaged in the same profession, formed usually to control entry into the profession, maintain standards, and represent the profession in discussions with other bodies.
The "flag ship" was a naval term for the ship carrying the commander of the fleet. But it also has come to mean the "finest, largest, or most important one of a group of things" (as per Merriam-Webster Dictionary). Therefore, a "flagship journal" is the most respected or prestigious journal of a discipline or of a professional association.
My own term, not in broad use, but very helpful in designing a research project. Find one, or maybe two, journal articles that have many characteristics of what you want your paper to have. Perhaps because of the topic, the research question, the methodology, or the findings. Use it as a framework to design much of your study, but then differ yours in some methodological way to compliment it, build on it, or even to challenge it.
*Of course, cite your anchor article appropriately (otherwise it borders on plagiarism!). See the sections on ASA and APA style for more tips on citing things appropriately.
AAA: American Anthropological Association (est. 1902) www.americananthro.org
AEA: American Economic Association (est. 1885) www.aeaweb.org
AHA: American Historical Association (est. 1884) www.historians.org
APSA: American Political Science Association (est. 1903) www.apsanet.org
APA: American Psychological Association (est. 1892) www.apa.org
ASA: American Sociological Association (est. 1905) www.asanet.org
ACJS: Academy of Criminal Justice Sciences (est. 1963) www.acjs.org
ASC: American Society of Criminology (est. 1941) www.asc41.com
ASHE: Association for the Study of Higher Education (est. 1976) www.ashe.ws
NASPA: Student Affairs Administrators in Higher Education (est. 1919) www.naspa.org
AOM: Academy of Management (est. 1936) www.aom.org
AMA: American Medical Association (est. 1847) www.ama-assn.org
NASW: National Association of Social Workers (est. 1955) www.socialworkers.org