At the money (ATM) - Financial definition
Concise definition of the term at the money
An option is said to be at the money when its strike is equal to the market price of the underlying asset.
Comprehensive definition of the term at the money
At the money is one of the three expressions which describe the relationship between an option's strike and the price of the underlying, the two others being in the money and out of the money.
Depending on the type of option (call or put), they have a different meaning:
A call is in the money when the option's strike is below the market price of the underlying, whereas a put is in the money when the strike is above the underlying's market price.
A call option is said out of the money when its strike is above the underlying's market price, whereas a put option is out of the money when its strike is below the market price of the underlying.