Querulous (adjective)

1. Constantly complaining or grumbling in a petulant or dissatisfied manner.
2. Having a tendency to complain or grumble excessively.
3. Expressing complaints or dissatisfaction in a peevish or whiney tone.

Origin:

Late 16th century: from latin querulus "complaining", from queri "to complain".

Examples:

1. The querulous customer was never satisfied and always had a complaint.
2. The querulous old man was known for his grumbling and complaining.
3. The querulous tone of the employee made it difficult for others to work with him.
4. The querulous voice of the child made it clear that he was unhappy about something.
5. The querulous behavior of the patient made it hard for the doctor to diagnose the problem.