An option is at-the-money (ATM) when its strike price is at, or very close to, the underlying’s current market price — the boundary point between in-the-money (ITM) and out-of-the-money (OTM).
Related Reading
See the full ITM/ATM/OTM breakdown for both Calls and Puts in ITM, ATM, OTM Explained: Understanding Option Moneyness.
