If "seized" means to grab or take hold of:
* Released: This is the most common opposite, meaning to let go.
* Freed: This suggests something was previously held captive or restricted.
If "seized" means to take control of:
* Surrendered: This implies giving up control willingly.
* Relinquished: This implies giving up control formally.
If "seized" means to become affected by a medical condition:
* Relieved: This suggests the condition has lessened or gone away.
* Recovered: This implies a full return to health.
If "seized" means to become stuck or jammed:
* Loosed: This suggests something is now free and moving again.
* Unstuck: This emphasizes the removal of the obstruction.
It's important to consider the specific context to choose the most accurate opposite.