The word “gruff” has several synonyms that can be used to describe someone's tone or manner.
One synonym is “rough”. When a person is gruff, they can be described as having a rough way of speaking or behaving. For example, “His tone was rough and unfriendly.” This implies a lack of smoothness or gentleness.
“Harsh” is another synonym. If someone is gruff, they may be harsh in their words or actions. “The teacher's criticism was harsh and made the student feel bad.” Harshness often conveys a sense of severity or sternness.
“Brusque” is also a good synonym for gruff. It means abrupt or curt in manner. “The manager was brusque with his employees and didn't have much patience.” Brusqueness suggests a lack of courtesy or warmth.
“Surly” can be used as well. A surly person is bad-tempered and unfriendly. “The clerk was surly and didn't answer my questions properly.” Surliness implies a sullen or grumpy attitude.
Finally, “gruffness” can sometimes be replaced by “curtness”. A curt response is short and to the point, often without any pleasantries. “Her reply was curt, as if she didn't want to talk to me.” Curtness indicates a lack of elaboration or friendliness.