Roose: Your command of the cavalry was impressive. Thanks to you, the false king Stannis Baratheon is dead. Do you know who struck the killing blow?
Roose: A shame. I'd reward the man. Still, a great victory.
The word "strike" has many different meanings and uses. It's a very common word in English.
In the first set of examples, "strike" is a verb which means to hit something or someone:
A pedestrian was struck and killed by an SUV.
A man was struck by lightning while playing golf.
Sarah said that if her husband ever strikes her she'll leave him.
Be careful when you strike a match.
As a verb "strike" can also mean that a person has a thought or a sudden inspiration:
You strike me as being a very ambitious person.
She strikes the other women in the office as being a little flirtatious around men.
That just struck me as a bad idea.
The word "striking" is an adjective. It means beautiful or impressive:
He has a striking physique.
She bears a striking resemblance to Marilyn Monroe.
As a noun, the word "strike" represents many different things:
A lightning strike hit the top of the tree.
The workers went on strike.
A pitcher tries to throw strikes in the game of baseball.
There are a few important expressions that use the word "strike."
That's a strike against you.
He struck gold.
They struck a deal.