The trouble with the term multiculturalism is that it obscures rather than clarifies. Here are three very different meanings.
Multiculturalism, as a sociological description of society.
Multiculturalism, as something that is permitted; i.e. different cultural norms are permitted to co-exist within the framework of a universalistic liberal society.
Multiculturalism, as an objective of government policy; i.e. encouraging and/or compelling individuals to be governed by their ethnic group (e.g. religious schools).
The first of the above is a fact. The second is desirable. The third is a form of Apartheid.