Webster 1913 definition
"(a) Of any right (called right in rem or jus in rem) of such a nature as to be available over its subject without reference to one person more than another, or, as generally expressed, a right competent, or available, against all persons. Rights in rem include not alone rights over physical property, but all rights available against all persons indifferently, as those of life, liberty, and reputation. (b) Of actions for recovering or reducing to possession or enjoyment a specific object, as in the enforcement of maritime liens against a vessel, which is made the defendant by a sort of personification. Most actions for the specific recovery of property in English and American law are in the nature of actions in personam against a person alleged to be unlawfully withholding the property."