a cart or wagon: a wheeled vehicle pulled by cattle to haul loads or carry people, as distinct from a war chariot
An agalah is a working cart: a wheeled platform pulled by oxen or cows to move heavy loads or people from place to place. It is the plain farm-and-household wagon of the ancient world, not a war machine. When Pharaoh sends wagons to bring Jacob's family down to Egypt, or when the ark is set on a new cart, this is the vehicle in view.
Because it was the standard heavy-hauler, the same cart turns up in vivid pictures: sin dragged along behind it on a rope, or a wagon so full of harvested grain that it groans under the weight. In farming, the cart or its heavy wheel is driven back and forth over the cut grain to thresh it, so the word can point to the implement as much as to the vehicle.
The one thing an agalah is not is a chariot. Hebrew keeps the fast, horse-drawn war and royal chariot under separate words. Where older translations say "chariot" (as with the wagons burned at the close of Psalm 46), the picture is really an army's slow baggage carts going up in flames.