The word curt can simply mean brief, usually in the context of speech. However, it has a connotation of being rude; if people are brief and nondescriptive, it can seem as if they don’t care to give anyone important information. People can construe this behavior as rude. In Harry Potter and the Prisoner of Azkaban, Uncle Vernon tries to communicate with Harry in inconspicuously, therefore, requiring him to be brief. To answer Harry’s questions, “Uncle Vernon nod[s] curtly behind Aunt Marge’s back.” (Rowling 19)
The picture below embodies Snape’s curt nature, as he frequently tells Harry to shut up, behave better, or just stay out of his personal life.