How is it determined that a party or movement is revisionist, and is there an amount of revisionism which does not to qualitative harm to it's goal?

Specifically I'm interested in an MLM answer as Maos development seems to be the most distinct, in as far as Socialism with Chinese Characteristics is a very different tradition from that of early European marxists. I've been called a revisionist because I most closely identify with Italian autonomous marxism, which places heavy emphasis on proletarian self-emancipation and working-place struggle. This is in stark contrast to the politics of Maoism, as far as I know, which places very little if any emphasis on the proletariat as a body, and much more on any social class which is exploited under capitalist/precapitalist society.

So my question is either what is the difference between these two, or if there is nothing actually un-Marxist in either, what exactly constitutes revisionism/a revisionist?