Definitions for labor union
Random House Webster's College Dictionary
an organization of wage earners or salaried employees for mutual aid and protection and for dealing collectively with employers; trade union.
Origin of labor union:
union, labor union, trade union, trades union, brotherhood(noun)
an organization of employees formed to bargain with the employer
"you have to join the union in order to get a job"
Kernerman English Learner's Dictionary
an organization that works to protect and improve conditions for workers
The labor union called a strike.
A continuous association of wage-earners for the purpose of maintaining or improving the conditions of their employment; a trade union.