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1. Being a member of or formed into a labour union
   "unionised labour";
   - organized, organised [Brit], unionized
    
2. Not converted into ions
   - nonionized, nonionised [Brit], unionized, nonionic

1. Recruit for a union or organize into a union
   "We don't allow people to come into our plant and try to unionise the workers";
   - unionize
    
2. Form or join a union
   "The auto workers decided to unionise";
   - unionize, organize, organise [Brit]

See also: union

Type of: enrol [Brit, Cdn], enroll [N. Amer], enter, fall in, get together, inscribe, join, recruit