The Vietnamese word "cằn nhằn" is a verb that means "to grumble" or "to complain" in a low voice, often in a way that expresses annoyance or dissatisfaction. It typically refers to expressing discontent about something in a somewhat persistent manner.
While "cằn nhằn" primarily means to grumble or complain, it can also imply a sense of annoyance that is somewhat persistent, suggesting that the person is not just upset but is vocalizing this upset frequently.