Masonic Service Association, a Freemason resource that publishes the monthly Short Talk Bulletin since 1923[1][2]

Methicillin-resistant Staphylococcus aureus, an antibiotic resistant strain of staphyloccus bacterium, AKA MRSA

MSA Garratt steam engine class of the Western Australian Government Railways

Multiple sequence alignment, an alignment of three or more biological sequences

Monash Student Association, the student government association of the Monash University, Melbourne, Australia

Medical savings account, an account where tax-deferred deposits can be made for medical expenses

Middle States Association of Colleges and Schools, a non-profit association dedicated to educational excellence and improvement through peer evaluation and accreditation.

Missouri Students Association, the student government association of the University of Missouri-Columbia

United States metropolitan area (Metropolitan Statistical Area), as defined by the Office of Management and Budget to designate a United States metropolitan area

Multiple system atrophy, a degenerative neurological disorder

Malaysia-Singapore Airlines, now Singapore Airlines and Malaysia Airlines separately

Literary Arabic (Modern Standard Arabic), the variety of Arabic used in most written media and some television talk shows in the Arabic-speaking world

Market Square Arena, an indoor arena in Indianapolis, Indiana built in 1974 and demolished in 2001

Mineralogical Society of America, a scientific organization founded for the advancement of mineralogy

Mail submission agent, an intermediary computer program or software agent which is used when sending email

Missouri Scholars Academy, a three-week residential summer program held on the University of Missouri's Columbia campus

Tobacco Master Settlement Agreement (Master Settlement Agreement), an agreement reached between U.S. States and major tobacco companies

Mississippi School of the Arts, a residential high school for the arts in Brookhaven, MS

Mycological Society of America, a scientific society promoting the study of fungi

Manchester School of Architecture, an architecture school in Greater Manchester, England

Mine Safety Appliances, a manufacturer of industrial safety clothing and equipment

Sulfonic acid (Methanesulfonic acid), an organic sulfonic acid

Muslim Students' Association, a group dedicated to Islamic societies on college campuses in Canada and the United States

Measurement Systems Analysis, the analysis of the entire process of obtaining measurements to ensure the integrity of data and to understand the implications of measurement error for decisions made about a product or process

Mapping Services Agreement, a licensing contract between local authorities in the United Kingdom and suppliers of geographic data

Master of Science in Administration, a post-graduate degree providing preparation for a variety of administrative positions

Muskrat Dam Airport, the IATA code for the airport at Muskrat Dam, Ontario, Canada

Motor Sports Association, the governing body for motorsport in the United Kingdom

Master of Accountancy (Master of Science in Accountancy), a post-graduate professional accounting degree

Mannitol Salt Agar, an agar useful in microbiology

Middle Stone Age, a period of African Prehistory between Early Stone Age and Late Stone Age, see also Mesolithic and Epipaleolithic

Modular Smart Array, a storage area network (SAN) technology manufactured by Hewlett-Packard (see also: HP StorageWorks)

Multi Source Agreement, used in the manufacturing of network optics. (eg [3]) see SFP_transceiver and XFP_transceiver