Directed backwards; behind.
[Latin retro, backwards.]
Some common examples are retroactive, taking effect from a date in the past; retrofit, to add a component or accessory to something that did not have it when manufactured; retrograde, directed or moving backwards; retrorocket, a rocket fired in the direction of travel to slow the craft down; retrospection, the action of looking back on or reviewing past events or situations, especially those in one's own life. A few words have the sense of ‘behind’: retrochoir, the interior of a cathedral or large church behind the high altar; retrosternal, behind the breastbone or sternum. However, in retrovirus, any of a group of RNA viruses which insert a DNA copy of their genome into the host cell in order to replicate, the form derives from the initial elements of reverse transcriptase.