“Strike price” is the valuation at which an asset/option can be bought at on on the open market immediately. Strike Price is also used to refer to the price at which an order was filled/settlement happened.
Example:
Phillip owns 10 Bitcoin. He place a buy order for them at $5,000 each coin. His order got filled a week later, while he was asleep. When he woke up he saw that his order was filled at $4,999. The strike price for his position was $4,999.