"Rough out" is a phrasal verb that means to create or draft something quickly or roughly. There are many synonyms that can be used in its place, depending on the specific context of the sentence. Some possible synonyms include sketch out, jot down, outline, blueprint, draft, rough sketch, rough draft, and preliminary version. These synonyms can be used interchangeably to convey the idea of quickly creating or outlining a rough idea. When choosing a synonym for "rough out", it is important to consider the connotations of each word and choose the one that best fits the tone and intention of the sentence.