Onomatopoeias are words that imitate or suggest the sounds associated with the thing or action it refers to. Antonyms for the word "onomatopoeias" would be words that are silent or do not imitate any sound. These can be words like calm, quiet, soft, silent, hushed, still, and motionless. While onomatopoeias bring life and excitement to language, silent words create a sense of calm and tranquility. They are perfect for creating a soothing atmosphere in a poem or writing piece. The use of antonyms for onomatopoeias adds depth and variation to writing, providing a balance of sounds and sensations for the readers.