The phrase "sell up" is primarily used in British English to mean selling one's business or property. Synonyms for this phrase include "liquidate," "dispose of," "divest," "offload," "transfer ownership," "sell off," "auction off," and "get rid of." These terms emphasize the act of selling or transferring ownership, often in order to raise funds. Other synonyms for "sell up" that emphasize the relinquishing of control over a property or business include "relinquish ownership," "abdicate control," and "transfer possession." Overall, there are many synonyms that can be used to convey the idea of selling one's business or property, which vary in tone and focus.