All of a sudden is an idiomatic expression used to describe something that happens unexpectedly or abruptly. However, there are many other synonyms for all of a sudden which can be effectively used to convey the same meaning. Some of the most commonly used synonyms for "all of a sudden" are suddenly, abruptly, unexpectedly, out of the blue, unanticipatedly, all at once, unforeseen, and startlingly. Using alternative expressions can help add variety and depth to your writing, making it more engaging and interesting. It also expands one's vocabulary, which is essential for effective communication and expression.