What does "survivorship" mean?

Survivorship: (Law) The right of a joint tenant, or other person who has a joint interest in an estate, to take the whole estate upon the death of other. Blackstone. Chance of survivorship, the chance that a person of a given age has of surviving another of a giving age; thus, by the Carlisle tables of mortality the chances of survivorship for two persons, aged 25 and 65, are 89 and 11 respectively, or about 8 to 1 that the elder die first.