Un-American is a pejorative term of U.S. political discourse which is applied to people or institutions in the United States seen as deviating from what are widely perceived to be fundamental American cultural and political values.
The most famous use is in the title of the House Un-American Activities Committee which was started to investigate alleged disloyalty and subversive activities on the part of private citizens, public employees, and those organizations suspected of having Communist ties. By 1959, former President Harry S. Truman had denounced the Committee as the "most un-American thing in the country today." The Committee lost considerable prestige as the 1960s progressed, and it was abolished by the House of Representatives in 1975.
The use and meaning of the term is by no means uniform in the US. Due in part to these historical associations with political abuses and jingoism, the attitudes of Americans toward the pejorative use of "Un-American" are often critical or suspicious. Moreover, Americans may vary widely in what they believe to be un-American.
Recent years have seen the term applied liberally regardless of political persuasion. It is most often used by a person commenting on the beliefs or actions of others that they believe is contrary to "American values." This highlights the wide variance in personal definitions of the phrase.
Additionally, some have described as un-American recent federal legislation in the U.S. that they view as an attack on civil liberties. The term (or similar sentiments) has been used by political supporters in the media to describe actions or beliefs that are critical of their candidate's policies.
The term "un-American" may be used in ad hominem attacks, meant to quash the arguments of American opponents by depicting them as subversive, unpatriotic or deviant. As a result, it is often used in a satirical or sarcastic manner; similarly, its frequent appearance in situations that do not merit its use has further diluted its original, pre-McCarthyism meaning.
Examples in current events
Plastic bag ban "Un-American"
On July 23, 2007, the City Council of Annapolis, Maryland convened to consider a bill banning plastic shopping bags from the city in order to protect the marine life of Chesapeake Bay. Safeway characterized the Annapolis bill and presumably the motives of its proponents, as "un-American": "At the hearing, a lobbyist for Safeway called the bill 'un-American,' saying it would take choices away from consumers."
Collective Bargaining Bill "Un-American"
On February 27, 2011, Connecticut Governor Dannel Malloy charged that the bill proposed by Wisconsin Governor Scott Walker to end the collective bargaining rights of public employees was "un-American". 
- House Un-American Activities Committee
- Hollywood blacklist
- "House Un-American Activities Committee". Elanor Roosevelt National Historic Site.
- Stephen J. Whitfield. The Culture of the Cold War. The Johns Hopkins University Press, 1996
- Hulse, Carl; Kate Zernike (2006-09-28). "Legislation Advances on Terrorism Trials". The New York Times. Retrieved 2007-08-13.
- Saunders, Debra J. "Anti-American and unaware". TownHall.com. Retrieved 2007-08-13.
- Urbina, Ian (2007-07-24). "Pressure Builds to Ban Plastic Bags in Stores". The New York Times. Retrieved 2007-08-13.
- Malloy: Wis. plan ‘un-American’ - POLITICO Live - POLITICO.com
- Enactments So Utterly Un-American
- Didn't Know I Was Unamerican.
- Un-American by Any Name
- Racial Profiling is Un-American
- An “Un-American Bill”: A Congressman Denounces Immigration Quotas
- "Buy American" is un-American
- Ken Lay's Un-American Activities
- "Shameful" Rush Limbaugh "Un-American"
- FOX Sics Its Dogs on "Un-American" Professors
- It's Downright Un-American
- Book declared unamerican by CNBC Managing Editor