Opposed to, or discouraging the formation of, trade unions(adjective)
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Use "antiunion" in a sentence
"Yet they were going to vote for Reagan, an antiunion president."
"Both accused Delta of interfering in the elections by intimidating workers with antiunion messages."
"Surely Mr. Trumka would not consider "un-American" or even "antiunion" the 1959 Executive Council of the AFL-CIO, which advised: "In terms of accepted collective bargaining procedures, government workers have no right beyond the authority to petition Congress—a right available to every citizen.""