Dictionary.net

(Leg.) A tenure of the same estate in unity of title, interest, and possession by two or more persons each of which is seised per my et per tout, with accession of the rights and interests of a deceased joint-tenant or jointtenants to the survivors or survivor. J. must subsist ab initio by the estate vesting in the joint-tenants at the same time. See Coparcenary; Jus accrescendi; Tenancy in common.

n. A tenure of estate by unity of interest, title, time, and possession, under which the survivor takes the whole.