OPOS'SUM, noun A quadruped of the genus Didelphis. It has a prehensile tail, like some of the monkeys, and is distinguished by a pouch or false belly, in which it protects and carries its young. The name is also given to other species of the genus, some of which want the pouch.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI