Definitions of waldo  [ˈwɔl doʊ, ˈwɒl-]  

1. A mechanical agent, such as a gripper arm, controlled by a human limb. When these were developed for the nuclear industry in the mid-1940s they were named after the invention described by Heinlein in the story, which he wrote in 1942. Now known by the more generic term telefactoring, this technology is of intense interest to NASA for tasks like space station maintenance.

2. At Harvard (particularly by Tom Cheatham and students), this is used instead of foobar as a metasyntactic variable and general nonsense word. See foo, bar, foobar, quux.