A Movement penalty in SMITE is caused by certain actions and will reduce a god's movement speed while they perform them.
There are 3 types of movement penalty: Backpedal, Stafing and Basic Attack penalties. The Backpedal penalty is applied when walking backward. The Strafing penalty is applied for moving sideways. The Basic Attack penalty is applied while firing basic attacks and persists for a short time afterwards. The Basic Attack penalty's potency is stronger for ranged gods than melee gods. None of these penalties are shown in the movement speed counter.
Some effects, such as Medusa's passive ability, will ignore or reduce the effect of these penalties. The effect Haste gained from certain abilities and from items like 
Hastened Katana will nullify the basic attack penalty.
According to community experiments:
- Backpedal penalty = 40% reduced†
- Strafing penalty = 20% reduced†
- Ranged Basic Attack penalty = 50% reduced†
- Melee Basic Attack penalty = 35% reduced†
†These numbers are based on player experimentation. No official values have been given.
Note: Only the highest movement penalty applies and is calculated after diminishing returns. This can cause the movement penalty to go past the movement speed floor.