unionism noun3 •The support of advocacy of a union, especially of a trade union.This isn't the time for militant unionism. If I were at ScotRail, in the current climate I'd trade a pay freeze [sic: pay rise?] for job security. — 2020 •Support for the North (the Union) during the American Civil War. •Support for the continuance of the United Kingdom (especially with respect to Northern Ireland). formsunionisms