|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.|
retroversion ret·ro·ver·sion (rět'rō-vûr'zhən, -shən)
A turning or tilting backward, as of the uterus.
The state of being turned or tilted back.
A condition in which the teeth are located in a position posterior to normal.