A collective noun that refers to the male genitalia. It is derived from the combination of the words "man" and "kangaroo" since male genitalia, like a kangaroo, has a pouch (see "scrotum").
History: Use of the word began in Tempe, AZ in 2008 where it quickly spread to southern California.
It's hot out today; my mangaroo is getting swampy!
Argh! He kicked me right in the mangaroo!