From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Terra-Freeze refers to the method that the Slugg's Demon Clan uses to dramatically cool down a planet.
After Slugg's Spaceship landed on Planet Earth, it was shown that his minions disliked heat and could not survive in sunlight for too long. The Terra-Freeze pod was launched into the atmosphere and a black cloud blanketed the whole planet. The global temperature dropped dramatically and the Earthlings began to suffer from the cold. The Terra-Freeze pod was finally destroyed when Son Goku fired the Genki Dama at Giant Slugg and he collided with it, causing both of them to explode.
It is unknown exactly how the process worked, but it appeared to take days at a time.