In the 19th century, 'communitarian' described people who experimented with communal living, as in Owenite and Fourierist settlements. Today the word usually names a philosophical school stressing the community's role in forming individuals.
In more detail
The word 'communitarian' was coined in 1841 by John Goodwyn Barmby, a Chartist, for utopian socialists and others who tried communal ways of life. Marx and Engels linked utopian socialism to 'communitarian socialism': founding small intentional communities as both means and end. The philosophical school gained currency only in the 1980s and concerns the individual's embeddedness in community, not communal property. The atlas uses the older sense for the 18th–19th-century experiments.