Conversion Legal Definition: A legal action against a person who found and converted someone else property to his own use. Related Terms: Trover , Ademption The action of conversion is a common law legal proceeding for damages by an owner of property against a defendant who came across the property and who, rather than return the property, converted that property to his own use or retained possession of the property or otherwise interfered with the property. The innocence of the defendant who took the property is not an issue. It is the conversion that gives rise to the cause of action. This common law action replaced the old action of trover by English law dated 1852. Compare with detinue. Unless otherwise noted, this page was written by Lloyd Duhaime of Duhaime.org Always looking up definitions? Save time with our search provider (modern browsers only) If you find an error or omission in Duhaime's Legal Dictionary, or if you have suggestion for a legal term, we'd love to hear from you!