The term 'Sign of Hostility' can be summarized by two crossword solutions: HISS (4 letters) and ICYSTARE (8 letters). A HISS is a sound made by expelling air through the teeth, often used to express disapproval or displeasure. An icy stare is a cold, hostile look that conveys anger or aggression. Both of these behaviors are signs of hostility and can be used to indicate that someone is feeling threatened or angry.