Anti-realism is a common philosophical term used for any philosophical notion which opposes the "real existence" of a particular type of thing. An anti-realist may deny the "existence" of other minds, the past or the future, universals, mathematical properties, moral categories, the material world, or even thought.
However the anti-realist does not deny the existence of each of these things in exactly the same sense. For example, a reductionist may argue that thought is nothing more than the arrangement of matter and energy, and thus deny the ontological reality of thought as a separate "thing," and therefore be called an anti-realist with respect to thought. At the same time someone like Berkley may argue precisely the opposite -- that the material world does not exist and is really nothing more than the sum of our perceptions -- and he would be called an anti-realist with regards to the external world.
Anti-Realism and the Problem of Universals:
Anti-Realism in YYY:
Anti-Realism in ZZZ: