There are several synonyms for the phrase "smashed up" that can be used to convey a similar meaning. One such synonym is "wrecked," which implies significant damage or destruction. Another option is "crushed," which suggests a forceful impact that flattens or destroys something. "Demolished" is another synonym that can be used to describe an object or structure that has been completely destroyed. Other options include "ruined," "broken," "shattered," or "fractured," all of which convey a sense of damage or destruction. These synonyms can be used interchangeably with "smashed up" depending on the context and intended meaning.