Final answer:
The term that describes an athletic trainer's failure to perform a required action under normal circumstances is 'omission'. It can lead to legal action, such as a malpractice lawsuit, if the inaction results in preventable harm.
Step-by-step explanation:
The term that refers to the failure of an athletic trainer to do something that should have been done under normal circumstances is omission. This is when a healthcare professional fails to perform an action that is part of the expected standard of care. In the context of an employment agreement, such an omission could lead to legal implications, like a malpractice lawsuit, if harm comes to a patient due to the athletic trainer's inaction. Malpractice specifically refers to improper or unethical conduct by a professional or official person, and an omission can certainly be an instance of malpractice if it results in harm that should have been preventable with proper care.