Phenomenal concepts have an ordinary and an edenic content of a concept. The ordinary content is, roughly, the folk interpretation of the phenomenal concept. The edenic content is a more thorough, idealized content (supposedly what one would arrive if one refines the phenomenal concept by analysis). Illusionism asserts that the edenic content does not refer (to something in reality), whereas the ordinary content may.
Relation to other metaphysical positions
According to the above definition, illusionism includes eliminativism, which rejects the latter possibility: Ordinary content also does not refer.