Wikipedia
In the communist lexicon, anti-revisionism is opposition to attempts to revise, modify, or abandon the fundamentals of revolutionary theory and practice. In this view, reformism within communism is rejected as representing dangerous concessions to communism's adversaries.
Because different political trends trace the historical roots of revisionism to different eras and leaders, there is significant disagreement today as to what constitutes anti-revisionism. Therefore, modern groups which describe themselves as anti-revisionist fall into several categories. They universally tend to oppose Trotskyism and de-Stalinization; however, some uphold the works of Marx, Engels, Lenin, Stalin, and Mao ( Maoism or Marxism–Leninism–Maoism), and some the works of Marx, Engels, Lenin and Stalin while rejecting Mao ( Marxism–Leninism). In addition, other groups uphold various less well-known historical leaders, such as Enver Hoxha ( Hoxhaism).
Historically, anti-revisionists presented a critique of the official Communist Parties "from the left" for having abandoned orthodox Marxism–Leninism (becoming "revisionist" and insufficiently revolutionary). The terminological disagreement can be confusing because different versions of a left-right political spectrum are used. Anti-revisionists consider themselves the ultimate leftists on a spectrum from communism on the left to imperialist capitalism on the right. But Stalinism is often labeled rightist within the communist spectrum and left communism leftist. In the wake of Khrushchev's speech to the 20th Congress of the C.P.S.U, the defense of Stalin and his legacy became a hallmark of anti-revisionism. In the 1970s the anti-revisionist movement expanded and diversified to encompass those communists who rejected a pro-Soviet orientation for one aligned either with Chinese or Albanian positions.
Anti-revisionism enjoyed its moment of greatest size and influence with numerous Marxist–Leninist and Maoist parties, groups and publications springing up around the world in the period which began with the Sino-Soviet split of the early 1960s. Its growth was greatly accelerated by international enthusiasm for the Cultural Revolution in China, but it began to decline in response to controversial Chinese foreign policy decisions in the last years of Mao Zedong's life, his death and the subsequent defeat of the Gang of Four. Some anti-revisionists responded to these events with little change to their theoretical orientation, others adjusted their orientation based on world events, while still remaining in the greater anti-revisionist milieu, while yet others took up a non-Trotskyist "left-wing" communism, independent of allegiance to foreign authorities or models, usually abandoning their claim to anti-revisionism in the process.