Defunct describes something that used to exist, but is now gone. A magazine that no longer publishes, like Sassy, the girl-power mag from the '90s, is defunct, for example.
Although defunct comes from the Latin word defunctus meaning "dead," it's not usually used to describe a person who's no longer with us, but rather institutions, projects, companies and political parties — you know, the boring stuff. Keep digging and you'll find that defunctus comes from defungi, meaning, "to finish," which is closer to how it's used today. Defunct can also refer to a rule or law that's no longer used or has become inactive, like prohibition.