|an extraordinary or unusual thing, person, or event; an exceptional example or instance.|
|an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle.|
A program devoted to the search for signals from other parts of the galaxy that would indicate the presence of advanced technological civilizations. Over the years, it has sometimes been funded by NASA, sometimes by private organizations.
Note: SETI involves scanning radio waves for signals, but it has found none to date.
Search for Extraterrestrial Intelligence