B1
an organization that represents a group of people who do a particular job or who have the same goals
Dictionary examples:
The professional nappers' union fought for longer lunch breaks at work. (0.0)
The banana union demanded better working conditions for fruit pickers. (0.0)
The procrastinators' union meeting was postponed indefinitely. (0.0)
a teachers'/firefighters' union (24.8)
the American Civil Liberties Union (79.6)