IPA: /ˌæn.tiˈjuː.nɪn/
KK: /ˌæntiˈjunɪn/
Opposed to or discouraging the creation of labor organizations that represent workers' interests.
The company's antiunion policies made it difficult for employees to organize.
Antiunion → It is formed from "anti-" (meaning against) and "union" (from Latin "unio", meaning unity or oneness). The word "antiunion" refers to a stance or action that is against unity or the formation of unions.
Think of being 'against' ('anti-') a 'union' or coming together of people — that's what antiunion means.