The Golden Dawn gave the seventh trump the letter Cheth, the sign Cancer, and the eighteenth path from Binah to Geburah. Cheth means a fence or an enclosure, and the pairing with a chariot, an enclosed thing that moves, is one of the neater fits in the system. Cancer, the sign of the shell, carries the same idea. As always the assignment is a late nineteenth-century construction and no fifteenth-century card-maker had it in view.
The card is read for directed force, and the readings divide on how confident that force is. The optimistic reading is victory, momentum, travel, and a will strong enough to hold a difficult course. The sceptical reading notices that the two animals drawing the chariot pull in different directions in most versions of the image, that they are not reined in any obvious way, and that the driver's control is therefore assumed rather than demonstrated. On that reading the card is about a person holding together, by force of will alone, something that would come apart if they relaxed.
Both readings are in general use and neither is a reversal of the other. Waite's reversed meanings run to defeat and to a collapse of the effort; readers working without reversals tend to read the strain into the upright card and let the surrounding cards say whether it holds.
The travel reading, incidentally, is old and stubborn, and cartomancers were giving it long before anyone attached a Hebrew letter to the card. It survives because it works often enough to keep being reported, which is how most divinatory conventions actually get established: not by derivation from a system, but by readers noticing what tends to happen and telling each other.