"Smashing up" is a colloquial term used to refer to the act of causing destruction or damage to something. There are several other synonyms that can be used in its place depending on the context and severity of the situation. Some synonyms include wrecking, shattering, demolishing, vandalizing, ravaging, or pulverizing. These words can be used to describe anything from physical destruction of property to the emotional damage caused by words or actions. However, it is important to use these words with caution and to consider the impact they may have on those affected by the damage or destruction.