Learner's definition of GRIEVANCE
1 : a feeling of having been treated unfairly
2 [count] : a reason for complaining or being unhappy with a situation 3 [count] : a statement in which you say you are unhappy or not satisfied with something
The union has filed a formal grievance [=complaint], accusing the company of unfair labor practices.
Several customers came to the front desk to air their grievances.