The phrase "mushed up" can refer to something that is mixed or blended together in a haphazard or unappealing way. There are several synonyms that can be substituted depending on the context of the sentence. For example, "mashed" or "pureed" can be used to describe food that has been blended until smooth. "Jumbled" or "scrambled" can be used to describe things that are mixed up in a disorganized way. "Crushed" or "smashed" can be used to describe something that has been forcibly broken down into smaller pieces. Overall, there are many synonyms for "mushed up" that can be used to add variety and precision to your writing.