actio de in rem verso

noun | \ ˈak-shē-ō-ˌdē-in-ˈrem-ˈvər-sō, ˈäk-tē-ō-ˌdā-in-ˈrem-ˈver-sō \ | ac·tio de in rem ver·so

1. : a doctrine equivalent to the common-law doctrine of unjust enrichment