Or just mis-worded, I guess. These ingame spell descriptions use words that have specific meanings within the game incorrectly, ex. substituting Action for Movement. Here's hoping someday there will be a patch; for now, this will have to do!

Your Variable Stats are the character stats that can be modified in battle by player or enemy actions. They are ACT (Action), MOV (Movement), ATK (Attack), and DEF (Defense).

Action determines how quickly your character moves on the Battle Gauge-- basically, how long it'll be before that character gets to move again.

Movement is how quickly your character can move around the battlefield. This can make the difference when you're trying to land a crit or kill an enemy before it does something you don't want it to.

Attack affects how much damage you can do with physical attacks.

Defense affects how much damage you take from physical attacks.

Speedy (Buff Spell)
Ingame Description: "Forest life-force ups movement ability"
Actual Effect: Increases Action. Does not affect Movement.

Stram (Debuff Spell)
Ingame Description: "Robs strength and drops enemy defense" [Mistranslated]
Actual Effect: Drops Attack. Does not affect Defense.

Freeze! (Debuff Spell)
Ingame Description: "Drops action with bone-chilling cold" [Mistranslated]
Actual Effect: Drops Movement, not Action.

Cold (Debuff Spell)
Ingame Description: "Drops movement with soul-chilling cold" [Mistranslated]
Actual Effect: Drops Action. Does not affect Movement.

Heel Crush (Millenia Special Move)
Ingame Description: "Deadly heel attack saps enemy spirit"
Actual Effect: In some games, enemies have fixed MP or SP that can run out, which is what this description accidentally implies-- but enemies in Grandia II can use spells and special moves as much as they'd like. This item doesn't steal anything from the enemy or give you any more SP. It decreases all the enemy's Variable Stats.