There are several synonyms for the phrase "more than can be used," some of which include surplus, excess, abundance, overflow, overabundance, oversupply, and superfluous. These terms are often used to indicate an excessive amount of something that is beyond what is necessary or useful. For instance, you might describe a business inventory that has an oversupply of products as "more than can be used" by customers. Similarly, a food pantry that has a surplus of donations might be described as having an abundance of supplies. No matter the context, these synonyms are all effective at conveying the idea of too much of something.