Incorrect spelling, explanation: siezing is an incorrect word, as it suggests the base word sieze, which simply does not exist. If you already know the pronunciation of seizing, you can also notice that the incorrect spelling would also be pronounced differently and it would not be clear to an English speaker.

Correct spelling, explanation: the word seize originates in the old French word seizir. The word underwent some changes, but it’s still relatively similar to its predecessor. Seizing is constructed by suffixing the English base word seize with -ing, where e changes to i because the -ing suffix always has to be whole, and e is silent either way, thus creating seizing.

Definition of seize:
adjective
1. to catch, grasp something
He stopped her from running by seizing her arm.
2. to understand something
I tried to learn my dog to roll over, but he’s incapable of seizing the concept of following commands.
3. to take something into possession, usually by force
If we can’t pay the mortgage off, the bank will be seizing our home.

Idioms with seize:
seize the moral high ground – to claim moral superiority over someone
My mom is such a hypocrite; she always tries seizing the moral high ground and then does something unacceptable herself.
seize the opportunity – to take on a chance to do something when it appears
There were sales up to 70% off, so I decided on seizing the opportunity and bought myself two pairs of shoes.