Final answer:
Administering medication to a competent patient who has refused it is categorized as battery. Battery is an intentional tort involving non-consensual contact, which in healthcare can include administering treatments against a patient's will.
Step-by-step explanation:
When discussing a nurse administering an antibiotic medication to a competent patient after the patient refuses, the action can be classified under the category of battery. Battery in the legal context refers to intentional and wrongful physical contact with a person without their consent.
It's important to note that the choice of antibiotic should always be based on culture and sensitivity tests to ensure effectiveness and prevent antibiotic resistance. In a real-world clinical setting, a medical professional would consult current practice guidelines and perform necessary tests before prescribing an antibiotic.