Make no sign means to refrain from indicating or showing any emotion or expression. The phrase is often used to describe a situation where a person needs to maintain composure or secrecy. There are several synonyms for this phrase, such as keeping mum, staying silent, remaining quiet, playing it cool, maintaining a poker face, and holding back emotions. These phrases imply a cautious approach to avoid exposing one's thoughts or feelings. They are often used in spy movies or situations where one needs to act discreetly. In summary, a person who makes no sign is one who is careful with their actions and expressions.