The word 'waviest' refers to something that is characterized by curves, undulations, or movements that resemble waves. Its antonyms are words that describe the opposite of this meaning. The opposite of 'waviest' could be 'straight,' which refers to something that has no curvature, irregularity, or bending. 'Still' is another antonym of 'waviest' which describes something that is motionless, immobile, or stagnant. Similarly, 'calm' could be an antonym of 'waviest,' indicating peace, tranquility, or serenity. Other possible antonyms of 'waviest' include 'stiff,' 'rigid,' 'unbending,' or 'unyielding,' which all indicate a lack of movement or flexibility.