1841, "make into a union" (transitive), from union + -ize. Sense "form into a trade union" is from 1887. Related: Unionized; unionizing.
We don't allow people to come into our plant and try to unionize the workers
The auto workers decided to unionize
uninvite
uninvited
uninviting
union
Union Jack
unionize
unipersonal
unipolar
unique
unisex
unisexual
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