unionism

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Belief in or support for a union or unions, especially a labor union or labor unions generally.
• noun The principles, theory, or system of a union or unions, especially a labor union or labor unions generally.
• noun The principle or theory of forming a union.
• noun The principles, theory, or system of a union, especially a trade union.
• noun Loyalty to the United Kingdom, especially in support of its sovereignty over Northern Ireland.
• noun Loyalty to the federal government of the United States during the Civil War.

from The Century Dictionary.

• noun The principle of uniting or combining; specifically, trade-unionism.
• noun Attachment or loyalty to the principle of union, or to some particular union; specifically, attachment or loyalty to the federal union known as the United States of America, and opposition to its rupture, as by the secession of the Southern States in 1861-5.
• noun In British politics, the principles or sentiments of the Unionists.

from the GNU version of the Collaborative International Dictionary of English.

• noun The sentiment of attachment to a federal union, especially to the federal union of the United States.
• noun The principles, or the system, of combination among workmen engaged in the same occupation or trade.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The support of advocacy of a union, especially of a trade union
• noun Support for the North (the Union) during the American Civil War
• noun Support for the continuance of the United Kingdom (especially with respect to Northern Ireland)

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the system or principles and theory of labor unions