When it comes to describing an eruption or sudden appearance of something, there are several synonyms available for "broken out." Some examples include "erupted," "burst forth," "sprung up," "emerged," "appeared suddenly," and "developed rapidly." Additionally, depending on the context, other phrases may be more appropriate, such as "flared up," "exploded," or "became visible." As with any synonym usage, it's important to consider the tone and intended meaning of the message to select the best option. By expanding your vocabulary options, you can enhance your writing and communication skills while conveying your ideas clearly and concisely.