The word "ceremonialize" represents the act of marking a significant event or occasion with a ceremonial observance or celebration. However, there are several antonyms for this word that suggest an absence of ceremony or formality. These antonyms include casualize, informalize, de-ceremonialize, and desacralize. "Casualize" is used to mean making something less formal or less rigorous. "Informalize" suggests the removal of formalities or strict adherence to protocol. "De-ceremonialize" implies the removal of ceremony or formalness from an event. "Desacralize," on the other hand, means to remove the religious or sacred significance from an event or ritual.