Retrograde
The stretch when a planet appears to drift backward through the zodiac. A trick of viewpoint, not a change in the orbit. In practice its matters come up for review rather than for launch.
All planets orbit the Sun in the same direction, but we watch from a moving platform. When Earth overtakes a slower planet, or a faster one overtakes us, that planet appears to slow, stop, and slide backward against the zodiac before resuming. That backward stretch is retrograde motion. Mercury does it about three times a year for three weeks at a stretch; Venus and Mars less often but for longer; the outer planets spend several months of every year retrograde.
Because a retrograde planet retraces its path, it lingers in one zone of the zodiac far longer than usual, and any aspect it makes there tends to repeat: an approach, a retrograde return, a final direct pass. Astrologers read the whole repetition as one extended process, and its theme is revision: second looks, unfinished business given another chance.
The folklore of dread, especially around Mercury, is a modern invention with little support in the serious literature. Nothing there forbids signing, traveling, or deciding while a planet is retrograde. The consistent counsel is milder: expect revisits, build in slack, and treat the season as editing time rather than launch time.