Move in waves is a phrase that describes a type of motion. The crossword solutions for this phrase are SURGE (5 letters), UNDULATE (8 letters), and BILLOW (6 letters). SURGE is a sudden, powerful forward movement, while UNDULATE is a smooth, wavelike motion. BILLOW is a large wave or swell of something, such as smoke or water. All three words describe a type of wave-like motion, which can be used to describe the phrase move in waves.