The term 'silent greeting' refers to a type of greeting that does not involve speaking. The crossword solutions for this term are WAVE (4 letters), NOD (3 letters), and SMILE (5 letters). A wave is a gesture made by moving one's hand back and forth, often used as a greeting or to say goodbye. A NOD is a gesture made by moving one's head up and down, often used to show agreement or acknowledgement. A SMILE is a facial expression made by curving the corners of one's mouth upwards, often used to express happiness or pleasure. All three of these gestures can be used as silent greetings.